* stable-3.0:
QueryAccount/QueryGroups: Enable retries
MergeSuperSet: Include change ID into error message
DeleteBranch/DeleteBranches: Disallow deletion of HEAD to prevent NPE
DeleteBranches: Disallow deletion of refs/meta/config branch
Change-Id: I9e5fb05c39b69847c8af9bca09a2d7d3979b184d