YARN-309. Changed NodeManager to obtain heart-beat interval from the ResourceManager. Contributed by Xuan Gong.
svn merge --ignore-ancestry -c 1463346 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1463347 13f79535-47bb-0310-9956-ffa450edef68