OAK-1295 - Recovery for missing _lastRev updates (WIP)

Avoid unnecessary updates of lastRev on parent where the lastRev is consistent and only lastRev for child needs to be fixed

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1583584 13f79535-47bb-0310-9956-ffa450edef68