YARN-365. Change NM heartbeat handling to not generate a scheduler event on each heartbeat. (Contributed by Xuan Gong)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1450007 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-Y-12345-trunk-gd