YARN-1908. Fixed DistributedShell to not fail in secure clusters. Contributed by Vinod Kumar Vavilapalli and Jian He.
svn merge --ignore-ancestry -c 1585849 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1585850 13f79535-47bb-0310-9956-ffa450edef68