OAK-1417: Processing pending observation events does not scale linearly with the number of events

Shortcut NamePathMapperImpl.getJcrPath() for the common case where
there are no local namespace remappings. This removes the O(log n)
cost of each Event.getPath() call, and helps drop the observed performance
closer to O(n) than O(n log n)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1567588 13f79535-47bb-0310-9956-ffa450edef68