svn merge -c 1616422 from trunk for HDFS-6809. Move Balancer's inner classes MovedBlocks and Matcher as to standalone classes and separates KeyManager from NameNodeConnector.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1616423 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1616426 from trunk for HDFS-6812. Remove addBlock and replaceBlock from DatanodeDescriptor.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1616427 13f79535-47bb-0310-9956-ffa450edef68