HDFS-5747. Merging r1557289 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1557291 13f79535-47bb-0310-9956-ffa450edef68
Merge r1557296 from trunk. YARN-1166. Fixed app-specific and attempt-specific QueueMetrics to be triggered by accordingly app event and attempt event. Contributed by Zhijie Shen

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1557297 13f79535-47bb-0310-9956-ffa450edef68