Fix sharing notes data in localStorage with all MRs

See merge request gitlab-org/gitlab-ce!32699

(cherry picked from commit 6dd99d82)

4fb658d1 Fix sharing localStorage with all MRs

Igor Drozdov authored 5 years ago and Mayra Cabrera committed 5 years ago

- Extract MR fields for notes into a separate serializer
- Check if pipelines are empty via count