YARN-1029. Added embedded leader election in the ResourceManager. Contributed by Karthik Kambatla.
svn merge --ignore-ancestry -c 1556103 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1556105 13f79535-47bb-0310-9956-ffa450edef68