HDFS-4877. Snapshot: fix the scenario where a directory is renamed under its prior descendant. Contributed by Jing Zhao.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1490421 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4867. metaSave NPEs when there are invalid blocks in repl queue. Contributed by Plamen Jeliazkov and Ravi Prakash.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1490433 13f79535-47bb-0310-9956-ffa450edef68
YARN-761. TestNMClientAsync fails sometimes (Zhijie Shen via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1490437 13f79535-47bb-0310-9956-ffa450edef68