Force the "latest revision" to be looked up on the master DB.

When fetching the latest revision for editing/updating,
we have to make sure it's actually the latest. Otherwise,
replication lag may cause unexpected edit conflicts.

Change-Id: I70ca8d9a839e64ee7f5ec9a3b5fa1a6d99c4d200
Merge "Force the "latest revision" to be looked up on the master DB."