Don't persist ApplicationSetting in test env

lib/gitlab/current_settings.rb

lib/gitlab/github_import/project_creator.rb

spec/controllers/health_check_controller_spec.rb

...features/admin/admin_disables_git_access_protocol_spec.rb

spec/features/admin/admin_health_check_spec.rb

spec/features/admin/admin_runners_spec.rb

spec/features/admin/admin_settings_spec.rb

spec/features/admin/admin_uses_repository_checks_spec.rb

spec/lib/gitlab/current_settings_spec.rb

spec/requests/api/internal_spec.rb

spec/spec_helper.rb