Resolve "Extract EE specific files/lines for some controller specs"

CE MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19089

What does this MR do?

This reduces the diff between CE and EE for several files under spec/controllers.

• 9ba43645 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/settings/integrations_controller_spec.rb [Rémy Coutable]
• 0f24804c 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/prometheus/metrics_controller_spec.rb [Rémy Coutable]
• 43d64abd 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/merge_requests_controller_spec.rb [Rémy Coutable]
• a0e82293 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/project_members_controller_spec.rb [Rémy Coutable]
• ff1a5892 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/issues_controller_spec.rb [Rémy Coutable]
• aa250a7f 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/imports_controller_spec.rb [Rémy Coutable]
• 63d9faed 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/group_links_controller_spec.rb [Rémy Coutable]
• d1ffc8b1 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/environments_controller_spec.rb [Rémy Coutable]
• bdae89f8 2018-05-22 | Reduce CE/EE diff in app/controllers/projects/clusters_controller.rb [Rémy Coutable]
• fc80b09c 2018-05-22 | Reduce CE/EE diff in spec/controllers/profiles/keys_controller_spec.rb [Rémy Coutable]
• c1503d33 2018-05-22 | Reduce CE/EE diff in spec/controllers/oauth/applications_controller_spec.rb [Rémy Coutable]
• cc7af2fc 2018-05-22 | Reduce CE/EE diff in spec/controllers/projects/boards_controller_spec.rb [Rémy Coutable]

Does this MR meet the acceptance criteria?

• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes #6045 (closed)