Use run_after_commit to avoid race condition, feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342/diffs#note_17038749

app/models/ci/pipeline.rb

@@ -84,7 +84,9 @@ module Ci
       end
 
       after_transition any => [:success, :failed] do |pipeline|
-        SendPipelineNotificationWorker.perform_async(pipeline.id)
+        pipeline.run_after_commit do
+          SendPipelineNotificationWorker.perform_async(pipeline.id)
+        end
       end
     end