Steps to Reproduce:
1.goto Infrastructure>Compute resources
2.Create EC2 compute resource
3.goto Infrastructure>Compute resources
4.delete the created compute resource

2017-05-23T11:30:56 24905450 [app] [I] Started DELETE "/compute_resources/6-ec2" for ::1 at 2017-05-23 11:30:56 +0000
2017-05-23T11:30:56 24905450 [app] [I] Processing by ComputeResourcesController#destroy as HTML
2017-05-23T11:30:56 24905450 [app] [I]   Parameters: {"authenticity_token"=>"...", "id"=>"6-ec2"}
2017-05-23T11:30:56 24905450 [app] [I] Current user: admin (administrator)
2017-05-23T11:30:56 24905450 [app] [D] Setting current user thread-local variable to admin
2017-05-23T11:30:56 24905450 [app] [D] Setting current organization thread-local variable to none
2017-05-23T11:30:56 24905450 [app] [D] Setting current location thread-local variable to none
2017-05-23T11:30:56 24905450 [app] [I] removing EC2: ec2 key foreman-6532cca12-32bf-4841-b323-5d205e563e99
D, [2017-05-23T11:30:56.334010 #14496] DEBUG -- : String does not start with the prefix 'encrypted-', so Foreman::Model::EC2 ec2 was not decrypted
2017-05-23T11:30:56 24905450 [app] [D] String does not start with the prefix 'encrypted-', so Foreman::Model::EC2 ec2 was not decrypted
2017-05-23T11:30:57 24905450 [app] [I] Completed 422 Unprocessable Entity in 1251ms (ActiveRecord: 15.8ms)
2017-05-23T11:30:57 24905450 [app] [F] 
 | ActiveRecord::RecordNotSaved (You cannot call create unless the parent is saved):
 |   app/models/concerns/key_pair_compute_resource.rb:44:in `destroy_key_pair'
 |   app/controllers/compute_resources_controller.rb:69:in `destroy'
 |   app/controllers/concerns/application_shared.rb:15:in `set_timezone'
 |   app/models/concerns/foreman/thread_session.rb:32:in `clear_thread'
 |   app/controllers/concerns/foreman/controller/topbar_sweeper.rb:12:in `set_topbar_sweeper_controller'
 |   /home/vagrant/projects/katello/lib/katello/params_parser_wrapper.rb:12:in `call'
 |   lib/middleware/catch_json_parse_errors.rb:8:in `call'
 |   lib/middleware/tagged_logging.rb:18:in `call'