Merge branch 'stable-3.6' into stable-3.7

* stable-3.6:
  Increase FetchOne coverage with unit tests
  Display the in-flight taskId when a runway conflict is detected
  Restore the fetching of all refs with empty delta
  Allow to filter out refs from the fetch-replication deltas
  Do not accumulate replication events with retrying tasks
  Add replication taskId during the execution of the fetch
  Allow FetchOne to retry the failed ref only

Change-Id: Ia13d007266eef97315d9a0961f3140e3bcdde9d5