OAK-1807 - ConstraintViolationException seen with multiple Oak/Mongo with ConcurrentCreateNodesTest

Updating logic to match closer to the one in benchmark. Now one worker thread per cluster is left to run for configured duration of time

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1594127 13f79535-47bb-0310-9956-ffa450edef68
OAK-1807 - ConstraintViolationException seen with multiple Oak/Mongo with ConcurrentCreateNodesTest

Enhancing the testcase and for now ignoring it. Issue still not reproducible with runtime of 10 mins

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1594128 13f79535-47bb-0310-9956-ffa450edef68