Reproduce:
In audit search-bar (e.g: user < email preferences < audit query builder) type `host = `
the auto-complete will failed with NoMethodError:

2016-08-21T15:21:54 5455fa1c [app] [F] 
 | NoMethodError (undefined method `scoped' for #<Class:0x0000000ced5b50>):
 |   app/models/host.rb:15:in `method_missing'
 |   app/controllers/concerns/foreman/controller/auto_complete_search.rb:13:in `auto_complete_search'
 |   app/controllers/concerns/application_shared.rb:14:in `set_timezone'
 |   app/models/concerns/foreman/thread_session.rb:32:in `clear_thread'
 |   lib/middleware/catch_json_parse_errors.rb:9:in `call'
 |   lib/middleware/tagged_logging.rb:18:in `call'