Merge branch 'stable-3.8' into stable-3.9

* stable-3.8:
  Fix ApplyObjectActionIT flakiness due to the wrong ref used
  Force async fetch as a fallback for sync replication
  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: I0c270644cfcc8e3b57fcf4bd674ea9ca24c36fda