Merge branch 'stable-3.4'

* stable-3.4:
  Manage removal of refs
  Use correct placeholders when logging in RevisionReader
  Honour the fetch ref-spec in replication.config
  Log the incoming git refs events for replication
  Fix pull-replication after the removal of Log4J from Gerrit
  Allow replication of refs that point to non-commit objects

Also fix the DeleteRefCommand and associated test to make it
compatible with Gerrit stable-3.5 and master branches.

Change-Id: I8d007c558fc7ebe8dbf1f8b390aad45117271270