OAK-50: user mgt (minor improvement)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1556543 13f79535-47bb-0310-9956-ffa450edef68
OAK-659: Move purge logic for transient changes below the NodeBuilder interface
additional test case

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1556544 13f79535-47bb-0310-9956-ffa450edef68