HADOOP-10786. Fix UGI#reloginFromKeytab on Java 8. Contributed by Stephen Chu.
HDFS-7383. DataNode.requestShortCircuitFdsForRead may throw NullPointerException. Contributed by Tsz Wo Nicholas Sze.
HADOOP-10786. Moved to hadoop-2.7.X.
HDFS-7383. Merged to branch-2.6 also.