YARN-1071. Enabled ResourceManager to recover cluster metrics numDecommissionedNMs after restarting. Contributed by Jian He.
svn merge --ignore-ancestry -c 1570469 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1570472 13f79535-47bb-0310-9956-ffa450edef68