OAK-1606: Omit warnings about accessing commit related info when external events are excluded

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1581856 13f79535-47bb-0310-9956-ffa450edef68
OAK-1496: Benchmark for concurrent file writes.

Patch by Amit Jain

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1581861 13f79535-47bb-0310-9956-ffa450edef68