OAK-1284: Root.commit(String, CommitHook) : CommitHook is not part of oak-api
Pass path of the target sub tree of the commit to Root.commit instead of a CommitHook

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1551250 13f79535-47bb-0310-9956-ffa450edef68