YARN-645. Moved RMDelegationTokenSecretManager from yarn-server-common to yarn-server-resourcemanager where it really belongs. Contributed by Jian He.
svn merge --ignore-ancestry -c 1479022 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1479026 13f79535-47bb-0310-9956-ffa450edef68