YARN-2494. Added NodeLabels Manager internal API and implementation. Contributed by Wangda Tan.

(cherry picked from commit db7f1653198b950e89567c06898d64f6b930a0ee)
HDFS-7198. Fix "unchecked conversion" warning in DFSClient#getPathTraceScope (cmccabe)
(cherry picked from commit 1ceb3269337e321e352b7cd9f946c5c52dcfddfa)
HDFS-7209. Populate EDEK cache when creating encryption zone. (Yi Liu via wang)

(cherry picked from commit d3d3d47202a18749eeebec22db759c19dd3e232c)