YARN-2264. Fixed a race condition in DrainDispatcher which may cause random test failures. Contributed by Li Lu

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1611126 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10839. Add unregisterSource() to MetricsSystem API. Contributed by Shanyu Zhao.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1611134 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6689. NFS doesn't return correct lookup access for direcories. Contributed by Brandon Li

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1611135 13f79535-47bb-0310-9956-ffa450edef68