HADOOP-11007. Reinstate building of ant tasks support. Contributed by
Jason Lowe.
(cherry picked from commit 99d7a452be91b3aefe9bcde9b51893ff6719742e)
Missing files from the previous commit of HADOOP-11007
Fix version in the pom.xml from HADOOP-11007 for branch-2.
HADOOP-11169. Fix DelegationTokenAuthenticatedURL to pass the connection Configurator to the authenticator. (Arun Suresh via wang)

(cherry picked from commit b2f619752355d4ef6733935c020f57c8a26d82e1)
HADOOP-11172. Improve error message in Shell#runCommand on OutOfMemoryError. (Yongjun Zhang via wang)

(cherry picked from commit 4b2834898cbcc66ffbf01b2fb10375e79a50d538)
Fixup for CHANGES.txt

(cherry picked from commit 0263656247f31a67347bea4b702869ddce21e7c4)
HDFS-7128. Decommission slows way down when it gets towards the end. Contributed by Ming Ma.

(cherry picked from commit 80cb472620f0a7889e311ca32212a42b95c6794e)
HADOOP-11166. Remove ulimit from test-patch.sh.

(cherry picked from commit 60f0f6fcde406ed15e9079e0ff34df744b09a844)
YARN-2649. Fixed TestAMRMRPCNodeUpdates test failure. Contributed by Ming Ma
(cherry picked from commit e16e25ab1beac89c8d8be4e9f2a7fbefe81d35f3)
YARN-913 service registry: YARN-2652 add hadoop-yarn-registry package under hadoop-yarn
HDFS-7203. Concurrent appending to the same file can cause data
corruption. Contributed by Kihwal Lee.
CHANGES.txt: move HADOOP-10404 underneath branch 2.6
HADOOP-11179. Java untar should handle the case that the file entry comes without its parent directory entry. Contributed by Craig Welch.

(cherry picked from commit a1690519317068d9855174752d22ff45f0e4c962)
HDFS-7202. Should be able to omit package name of SpanReceiver on "hadoop trace -add" (iwasakims via cmccabe)
(cherry picked from commit d996235285e5047f731e3d3fc4c6e6214caa10aa)
HADOOP-11161. Expose close method in KeyProvider to give clients of Provider implementations a hook to release resources. Contribued by Arun Suresh.
(cherry picked from commit d9556e873ef4d3e68c4f0c991f856d1faa747f07)
HADOOP-11133. Should trim the content of keystore password file for JavaKeyStoreProvider (Yi Liu via umamahesh)
(cherry picked from commit 8d7c54967d5a08cdff75a782998ee89e7537b5c4)
HDFS-7217. Better batching of IBRs. Contributed by Kihwal Lee.
(cherry picked from commit db71bb54bcc75b71c5841b25ceb03fb0218c6d4f)
HADOOP-11175. Fix several issues of hadoop security configuration in user doc. Contributed by Yi Liu.

(cherry picked from commit 1123a06e3658f26228f1eedaed796aca8efc7bad)
YARN-2493. Added user-APIs for using node-labels. Contributed by Wangda Tan.

(cherry picked from commit 180afa2f86f9854c536c3d4ff7476880e41ac48d)
HDFS-7195. Update user doc of secure mode about Datanodes don't require root or jsvc. Contributed by Chris Nauroth.