OAK-1484: additional observation queue jmx attributes
Simplify logic around handling full queues

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1579233 13f79535-47bb-0310-9956-ffa450edef68
OAK-1484: additional observation queue jmx attributes
Add time series for the maximum number of pending revisions in the observation revision queue

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1579234 13f79535-47bb-0310-9956-ffa450edef68