When on the New Host page with OS details all configured, the "Resolve" provisioning templates button shows a warning of "Sorry but no templates were configured." and Foreman logs:

2016-06-09T13:07:33 [app] [I] Started POST "/hosts/template_used&provisioning=build" for 127.0.0.1 at 2016-06-09 13:07:33 +0100
2016-06-09T13:07:33 [app] [F] 
 | ActionController::RoutingError (No route matches [POST] "/hosts/template_used&provisioning=build"):
 |   actionpack (4.2.6) lib/action_dispatch/middleware/debug_exceptions.rb:21:in `call'
 |   actionpack (4.2.6) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
 |   railties (4.2.6) lib/rails/rack/logger.rb:38:in `call_app'
 |   railties (4.2.6) lib/rails/rack/logger.rb:22:in `call'
 |   quiet_assets (1.1.0) lib/quiet_assets.rb:27:in `call_with_quiet_assets'
 |   actionpack (4.2.6) lib/action_dispatch/middleware/request_id.rb:21:in `call'
 |   rack (1.6.4) lib/rack/methodoverride.rb:22:in `call'
 |   rack (1.6.4) lib/rack/runtime.rb:18:in `call'
 |   activesupport (4.2.6) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
 |   rack (1.6.4) lib/rack/lock.rb:17:in `call'
 |   actionpack (4.2.6) lib/action_dispatch/middleware/static.rb:120:in `call'
 |   rack (1.6.4) lib/rack/sendfile.rb:113:in `call'
 |   railties (4.2.6) lib/rails/engine.rb:518:in `call'
 |   railties (4.2.6) lib/rails/application.rb:165:in `call'
 |   railties (4.2.6) lib/rails/railtie.rb:194:in `public_send'
 |   railties (4.2.6) lib/rails/railtie.rb:194:in `method_missing'
 |   rack (1.6.4) lib/rack/urlmap.rb:66:in `block in call'
 |   rack (1.6.4) lib/rack/urlmap.rb:50:in `each'
 |   rack (1.6.4) lib/rack/urlmap.rb:50:in `call'
 |   rack (1.6.4) lib/rack/lock.rb:17:in `call'
 |   rack (1.6.4) lib/rack/content_length.rb:15:in `call'
 |   rack (1.6.4) lib/rack/handler/webrick.rb:88:in `service'
 |   /home/dcleal/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/webrick/httpserver.rb:140:in `service'
 |   /home/dcleal/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/webrick/httpserver.rb:96:in `run'
 |   /home/dcleal/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/webrick/server.rb:296:in `block in start_thread'
 |   logging (2.1.0) lib/logging/diagnostic_context.rb:450:in `block in create_with_logging_context'
 | 
 | 
2016-06-09T13:07:33 [app] [I]   Rendered /home/dcleal/.rvm/gems/ruby-2.3.0@foreman/gems/actionpack-4.2.6/lib/action_dispatch/middleware/templates/rescues/_trace.text.erb (0.5ms)
2016-06-09T13:07:33 [app] [I]   Rendered /home/dcleal/.rvm/gems/ruby-2.3.0@foreman/gems/actionpack-4.2.6/lib/action_dispatch/middleware/templates/rescues/routing_error.text.erb (6.3ms)

This works prior to ticket #15223 where it generates a valid path:

2016-06-09T13:08:16 [app] [I] Started POST "/hosts/template_used?provisioning=build" for 127.0.0.1 at 2016-06-09 13:08:16 +0100
2016-06-09T13:08:16 [app] [I] Processing by HostsController#template_used as */*