OAK-1332: Large number of changes to the same node can fill observation queue

Handle added and removed nodes instantly if we're not interested in
changes in those subtrees and thus won't need the deferred subtree diffs

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1561818 13f79535-47bb-0310-9956-ffa450edef68