Merge r1521560 from trunk to branch-2 for YARN-1098. Separate out RM services into Always On and Active (Karthik Kambatla via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1521562 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5020. Compile failure with JDK8 (Trevor Robinson via tgraves)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1521584 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5085. Merge change r1521601 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1521607 13f79535-47bb-0310-9956-ffa450edef68
YARN-1119. Add ClusterMetrics checks to tho TestRMNodeTransitions tests (Mit Desai via jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1521623 13f79535-47bb-0310-9956-ffa450edef68