YARN-2830. Add backwords compatible ContainerId.newInstance constructor. Contributed by Jonathan Eagles.

(cherry picked from commit 43cd07b408c6613d2c9aa89203cfa3110d830538)
HADOOP-10786. Fix UGI#reloginFromKeytab on Java 8. Contributed by Stephen Chu.
Revert "HADOOP-10786. Fix UGI#reloginFromKeytab on Java 8. Contributed by Stephen Chu."

Moving this to 2.7 only.
HDFS-7383. DataNode.requestShortCircuitFdsForRead may throw NullPointerException. Contributed by Tsz Wo Nicholas Sze.

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
Fix broken download of directories

(cherry picked from commit 745c9a01243b8eefc72d89d1164d7d010b80983b)