OAK-1788: ConcurrentConflictTest fails occasionally

Merge r1602179 from trunk

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1602810 13f79535-47bb-0310-9956-ffa450edef68
OAK-1892: OrderedIndexConcurrentClusterIT takes too long

Merge r1602809 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/branches/1.0@1602811 13f79535-47bb-0310-9956-ffa450edef68