Merge branch 'stable-3.6' into stable-3.7

* stable-3.6:
  Fix ApplyObjectActionIT flakiness due to the wrong ref used
  Index change asynchronously upon refs replicated event
  Address follow-up comments to Change 396868
  Introduce wait for replication events to reduce flaky tests
  Fail apply-object on change /meta when missing patch-set

Change-Id: Ic1b25814f3ec80605c8facd2ae12b39c7708af9b