merge -c 1460001 from trunk to branch-2 to fix YARN-470. Support a way to disable resource monitoring on the NodeManager. Contributed by Siddharth Seth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1460002 13f79535-47bb-0310-9956-ffa450edef68