YARN-2496. Enhanced Capacity Scheduler to have basic support for allocating resources based on node-labels. Contributed by Wangda Tan.
YARN-2500. Ehnaced ResourceManager to support schedulers allocating resources based on node-labels. Contributed by Wangda Tan.

(cherry picked from commit f2ea555ac6c06a3f2f6559731f48711fff05d3f1)