Description of problem:
Enabling deep merge causes NoMethodError: undefined method `each_pair' with some kind of group-level overrides.

Steps to Reproduce:
1. Add https://forge.puppetlabs.com/stbenjam/hash_resources module to any puppet env;
2. Specify parameter type for smart class parameter "resources" as "hash";
3. Enable "Merge overrides";
4. On group level override "resources" value with the following:

keepalived::vrrp::instance:
  VR_AP:
    state: EQUAL
    interface: <%= @host.primary_interface.identifier %>
    virtual_router_id: 76
    priority: 1
    advert_int: 1
    auth_type: PASS
    auth_pass: KeeOpros
    virtual_ipaddress:
    - 10.8.36.76/23

5. Add host to that group;
6. On foreman host execute "/etc/puppet/node.rb hostname_with_overriden_resources"

Actual results:

Error retrieving node hostname: Net::HTTPPreconditionFailed
Check Foreman's /var/log/foreman/production.log for more information.

production.log:

2015-10-09 14:14:46 [app] [I] Processing by HostsController#externalNodes as YML
2015-10-09 14:14:46 [app] [I]   Parameters: {"name"=>"hostname"}
2015-10-09 14:14:47 [app] [W] Failed to generate external nodes for hostname
 | NoMethodError: undefined method `each_pair' for #<String:0x007fbe6eeae5f0>
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/core_ext/hash/deep_merge.rb:15:in `deep_merge!'
 | /usr/share/foreman/app/services/classification/base.rb:216:in `block in update_hash_matcher'
 | /usr/share/foreman/app/services/classification/base.rb:211:in `each'
 | /usr/share/foreman/app/services/classification/base.rb:211:in `update_hash_matcher'
 | /usr/share/foreman/app/services/classification/base.rb:60:in `block in values_hash'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/relation/delegation.rb:6:in `each'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/relation/delegation.rb:6:in `each'
 | /usr/share/foreman/app/services/classification/base.rb:39:in `values_hash'
 | /usr/share/foreman/app/services/classification/class_param.rb:5:in `enc'
 | /usr/share/foreman/app/models/host/managed.rb:833:in `lookup_keys_class_params'
 | /usr/share/foreman/app/models/host/managed.rb:379:in `info'
 | /opt/rh/ruby193/root/usr/share/gems/gems/katello-2.3.1/app/models/katello/concerns/host_managed_extensions.rb:37:in `info_with_katello'
 | /usr/share/foreman/app/controllers/hosts_controller.rb:175:in `block (2 levels) in externalNodes'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/mime_responds.rb:196:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/mime_responds.rb:196:in `respond_to'
 | /usr/share/foreman/app/controllers/hosts_controller.rb:173:in `externalNodes'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/abstract_controller/base.rb:167:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/rendering.rb:10:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/abstract_controller/callbacks.rb:18:in `block in process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:583:in `block (4 levels) in _run__3517729025394552365__process_action__3937467537153203590__callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_11924'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:326:in `around'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:310:in `_callback_around_2443'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_11924'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:560:in `block (3 levels) in _run__3517729025394552365__process_action__3937467537153203590__callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_11923'
 | /usr/share/foreman/app/controllers/concerns/application_shared.rb:13:in `set_timezone'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_11923'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:559:in `block (2 levels) in _run__3517729025394552365__process_action__3937467537153203590__callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_11922'
 | /usr/share/foreman/app/models/concerns/foreman/thread_session.rb:32:in `clear_thread'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_11922'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:437:in `block in _run__3517729025394552365__process_action__3937467537153203590__callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:215:in `block in _conditional_callback_around_11921'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:326:in `around'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:310:in `_callback_around_13'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:214:in `_conditional_callback_around_11921'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:403:in `_run__3517729025394552365__process_action__3937467537153203590__callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:405:in `__run_callback'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:81:in `run_callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/abstract_controller/callbacks.rb:17:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/rescue.rb:29:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/notifications.rb:123:in `block in instrument'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/notifications.rb:123:in `instrument'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/instrumentation.rb:29:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/railties/controller_runtime.rb:18:in `process_action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/abstract_controller/base.rb:121:in `process'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/abstract_controller/rendering.rb:45:in `process'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal.rb:203:in `dispatch'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_controller/metal.rb:246:in `block in action'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/routing/route_set.rb:73:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/routing/route_set.rb:36:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/journey-1.0.4/lib/journey/router.rb:68:in `block in call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/journey-1.0.4/lib/journey/router.rb:56:in `each'
 | /opt/rh/ruby193/root/usr/share/gems/gems/journey-1.0.4/lib/journey/router.rb:56:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/routing/route_set.rb:600:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/apipie-rails-0.2.6/lib/apipie/extractor/recorder.rb:97:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/apipie-rails-0.2.6/lib/apipie/middleware/checksum_in_headers.rb:27:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/etag.rb:23:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/conditionalget.rb:25:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/head.rb:14:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/params_parser.rb:21:in `call'
 | /usr/share/foreman/lib/middleware/catch_json_parse_errors.rb:9:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/flash.rb:242:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/session/abstract/id.rb:205:in `context'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/session/abstract/id.rb:200:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/cookies.rb:339:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/query_cache.rb:64:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:405:in `_run__196417110406150970__call__2338207417472428176__callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:405:in `__run_callback'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/callbacks.rb:81:in `run_callbacks'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/callbacks.rb:27:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/railties-3.2.8/lib/rails/rack/logger.rb:26:in `call_app'
 | /opt/rh/ruby193/root/usr/share/gems/gems/railties-3.2.8/lib/rails/rack/logger.rb:16:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/request_id.rb:22:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/methodoverride.rb:21:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/runtime.rb:17:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/activesupport-3.2.8/lib/active_support/cache/strategy/local_cache.rb:72:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/lock.rb:15:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/actionpack-3.2.8/lib/action_dispatch/middleware/static.rb:62:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-cache-1.2/lib/rack/cache/context.rb:136:in `forward'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-cache-1.2/lib/rack/cache/context.rb:245:in `fetch'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-cache-1.2/lib/rack/cache/context.rb:185:in `lookup'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-cache-1.2/lib/rack/cache/context.rb:66:in `call!'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-cache-1.2/lib/rack/cache/context.rb:51:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/railties-3.2.8/lib/rails/engine.rb:479:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/railties-3.2.8/lib/rails/application.rb:223:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/railties-3.2.8/lib/rails/railtie/configurable.rb:30:in `method_missing'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/builder.rb:134:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/urlmap.rb:64:in `block in call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/urlmap.rb:49:in `each'
 | /opt/rh/ruby193/root/usr/share/gems/gems/rack-1.4.1/lib/rack/urlmap.rb:49:in `call'
 | /usr/share/gems/gems/passenger-4.0.18/lib/phusion_passenger/rack/thread_handler_extension.rb:77:in `process_request'
 | /usr/share/gems/gems/passenger-4.0.18/lib/phusion_passenger/request_handler/thread_handler.rb:140:in `accept_and_process_next_request'
 | /usr/share/gems/gems/passenger-4.0.18/lib/phusion_passenger/request_handler/thread_handler.rb:108:in `main_loop'
 | /usr/share/gems/gems/passenger-4.0.18/lib/phusion_passenger/request_handler.rb:441:in `block (3 levels) in start_threads'
 | /opt/rh/ruby193/root/usr/share/gems/gems/logging-1.8.2/lib/logging/diagnostic_context.rb:323:in `call'
 | /opt/rh/ruby193/root/usr/share/gems/gems/logging-1.8.2/lib/logging/diagnostic_context.rb:323:in `block in create_with_logging_context'
2015-10-09 14:14:47 [app] [I]   Rendered text template (0.0ms)
2015-10-09 14:14:47 [app] [I] Completed 412 Precondition Failed in 285ms (Views: 1.5ms | ActiveRecord: 49.8ms)

Expected results:
Correct node definition.

Additional info:

Seems to be important for me.

If I'll remove "interface: <%= @host.primary_interface.identifier %>" line from "override" value on group-level parameters than I can see that value turns to a string:

--- ! "keepalived::vrrp::instance:\r\n  VR_AP:\r\n    state: EQUAL\r\n    virtual_router_id:
  76\r\n    priority: 1\r\n    advert_int: 1\r\n    auth_type: PASS\r\n    auth_pass:
  KeeOpros\r\n    virtual_ipaddress:\r\n    - 10.8.36.76/23"

If I'll override this value from "Edit Puppet Class" page AND remove "interface: <%= @host.primary_interface.identifier %>" line then everything works as expected.

Package versions:

# rpm -qa | grep foreman
ruby193-rubygem-puppetdb_foreman-0.1.2-1.el7.noarch
ruby193-rubygem-foreman_gutterball-0.0.1-1.201507061443gitb9974c7.git.0.64e9626.el7.noarch
ruby193-rubygem-foreman_templates-2.0.0-1.el7.noarch
foreman-1.9.2-1.el7.noarch
foreman-gce-1.9.2-1.el7.noarch
foreman-postgresql-1.9.2-1.el7.noarch
rubygem-hammer_cli_foreman_bootdisk-0.1.3-1.el7.noarch
foreman-vmware-1.9.2-1.el7.noarch
foreman-ec2-1.9.2-1.el7.noarch
foreman-selinux-1.9.2-1.el7.noarch
ruby193-rubygem-foreman_bootdisk-6.0.0-1.el7.noarch
ruby193-rubygem-foreman-tasks-0.7.3-1.fm1_9.el7.noarch
ruby193-rubygem-foreman_docker-1.4.1-1.fm1_9.el7.noarch
ruby193-rubygem-foreman_setup-3.0.2-1.fm1_9.el7.noarch
rubygem-hammer_cli_foreman-0.3.0-1.el7.noarch
rubygem-hammer_cli_foreman_docker-0.0.3-2.el7.noarch
ruby193-rubygem-foreman_remote_execution-0.0.4-1.fm1_9.el7.noarch
foreman-compute-1.9.2-1.el7.noarch
foreman-libvirt-1.9.2-1.el7.noarch
ruby193-rubygem-foreman_default_hostgroup-3.0.0-1.el7.noarch
foreman-proxy-1.9.2-1.el7.noarch
rubygem-hammer_cli_foreman_tasks-0.0.7-1.el7.noarch
ruby193-rubygem-foreman_hooks-0.3.8-1.el7.noarch
ruby193-rubygem-foreman_discovery-4.0.0-1.fm1_9.el7.noarch
foreman-debug-1.9.2-1.el7.noarch
foreman-ovirt-1.9.2-1.el7.noarch