YARN-981. Fixed YARN webapp so that /logs servlet works like before. Contributed by Jian He.
svn merge --ignore-ancestry -c 1518030 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1518031 13f79535-47bb-0310-9956-ffa450edef68