HDFS-6578: Merging r1604942 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604943 13f79535-47bb-0310-9956-ffa450edef68
Merge r1604949 from trunk. YARN-2191. Added a new test to ensure NM will clean up completed applications in the case of RM restart. Contributed by Wangda Tan

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604950 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10659: Merging r1604955 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604956 13f79535-47bb-0310-9956-ffa450edef68