HDFS-6231. Merging change r1586553 from branch-2 to branch-2.4

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1586563 13f79535-47bb-0310-9956-ffa450edef68
YARN-1926. Changed DistributedShell to use appIDs as unique identifiers for HDFS paths and thus avoid test failures on Windows. Contributed by Varun Vasudev.
svn merge --ignore-ancestry -c 1586562 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1586565 13f79535-47bb-0310-9956-ffa450edef68