YARN-2274. FairScheduler: Add debug information about cluster capacity, availability and reservations. (kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1610542 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6378. Merging change r1610543 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1610545 13f79535-47bb-0310-9956-ffa450edef68