HBASE-22799 Generate CHANGES.md and RELEASENOTES.md for 2.1.6

[Apache9]

No description provided.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
0	reexec	78	Docker mode activated.
		_ Prechecks _
+1	dupname	0	No case conflicting files found.
+1	@author	0	The patch does not contain any @author tags.
		_ branch-2.1 Compile Tests _
		_ Patch Compile Tests _
+1	whitespace	0	The patch has no whitespace issues.
		_ Other Tests _
+1	asflicense	22	The patch does not generate ASF License warnings.
		188

Subsystem	Report/Notes
Docker	Client=19.03.1 Server=19.03.1 base: https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-491/1/artifact/out/Dockerfile
GITHUB PR	#491
Optional Tests	dupname asflicense
uname	Linux 2c9eedcdb871 4.4.0-154-generic #181-Ubuntu SMP Tue Jun 25 05:29:03 UTC 2019 x86_64 GNU/Linux
Build tool	maven
Personality	/home/jenkins/jenkins-slave/workspace/HBase-PreCommit-GitHub-PR_PR-491/out/precommit/personality/provided.sh
git revision	branch-2.1 / e27ef92
Max. process+thread count	47 (vs. ulimit of 10000)
modules	C: . U: .
Console output	https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-491/1/console
versions	git=2.11.0 maven=2018-06-17T18:33:14Z)
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