Merge branch 'optimize-project-ci-services' into 'master'

Optimize Project#ci_service(s)

Related issue: gitlab-org/gitlab-ce#14186

See merge request !3158

app/models/project.rb

@@ -528,11 +528,11 @@ class Project < ActiveRecord::Base
   end
 
   def ci_services
-    services.select { |service| service.category == :ci }
+    services.where(category: :ci)
   end
 
   def ci_service
-    @ci_service ||= ci_services.find(&:activated?)
+    @ci_service ||= ci_services.reorder(nil).find_by(active: true)
   end
 
   def jira_tracker?