HDFS-3245. Add metrics and web UI for cluster version summary. Contributed by Ravi Prakash.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1517937 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5128. Allow multiple net interfaces to be used with HA namenode RPC server. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1517981 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5132. Deadlock in NameNode between SafeModeMonitor#run and DatanodeManager#handleHeartbeat. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1517989 13f79535-47bb-0310-9956-ffa450edef68
Adding the new test file for HDFS-3245 that was accidentally dropped

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1517994 13f79535-47bb-0310-9956-ffa450edef68