Merge branch 'stable-3.1'

* stable-3.1:
  Fix mocks in ProjectVersionRefUpdateTest
  Re-create global-refdb project versions when missing
  Add unit-test for SubscriberMetrics
  Silence exception when repository is not found
  Generate project version logging for analyzing replication lag
  Rely on replication for version ref propagation

Change-Id: I5f62e452339da023dba5794490c9555792440b86