YARN-2247. Made RM web services authenticate users via kerberos and delegation token. Contributed by Varun Vasudev.
svn merge --ignore-ancestry -c 1613821 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.5@1613823 13f79535-47bb-0310-9956-ffa450edef68