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