Merge branch 'perform-ci-build-auth-always-on-primary-ce' into 'master'

Bring back the EE changes to CE to authentication of builds

See merge request gitlab-org/gitlab-ce!19391

lib/gitlab/auth.rb

@@ -240,7 +240,7 @@ module Gitlab
         return unless login == 'gitlab-ci-token'
         return unless password
 
-        build = ::Ci::Build.running.find_by_token(password)
+        build = find_build_by_token(password)
         return unless build
         return unless build.project.builds_enabled?
 
@@ -301,6 +301,12 @@ module Gitlab
 
         REGISTRY_SCOPES
       end
+
+      private
+
+      def find_build_by_token(token)
+        ::Ci::Build.running.find_by_token(token)
+      end
     end
   end
 end