HBASE-25816: Improve the documentation of Architecture section of reference guide

[Kota-SH]

This PR refers to https://issues.apache.org/jira/browse/HBASE-25816

While going through the reference guide, I found these small changes that can be made to the documentation of the "Architecture" part of it. Hence I'm filing this Jira to track those changes.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	0m 27s	Docker mode activated.
-0 ⚠️	yetus	0m 4s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
		_ Patch Compile Tests _
		_ Other Tests _
		1m 40s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/artifact/yetus-jdk11-hadoop3-check/output/Dockerfile
GITHUB PR	#3211
JIRA Issue	HBASE-25816
Optional Tests
uname	Linux 118e9f1e0ad1 4.15.0-58-generic #64-Ubuntu SMP Tue Aug 6 11:12:41 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 6c65314
Max. process+thread count	55 (vs. ulimit of 30000)
modules	C: . U: .
Console output	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/console
versions	git=2.17.1 maven=3.6.3
Powered by	Apache Yetus 0.12.0 https://yetus.apache.org

This message was automatically generated.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	0m 28s	Docker mode activated.
-0 ⚠️	yetus	0m 3s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
		_ Patch Compile Tests _
		_ Other Tests _
		1m 38s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/artifact/yetus-jdk8-hadoop3-check/output/Dockerfile
GITHUB PR	#3211
JIRA Issue	HBASE-25816
Optional Tests
uname	Linux edf8eac6b372 4.15.0-58-generic #64-Ubuntu SMP Tue Aug 6 11:12:41 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 6c65314
Max. process+thread count	47 (vs. ulimit of 30000)
modules	C: . U: .
Console output	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/console
versions	git=2.17.1 maven=3.6.3
Powered by	Apache Yetus 0.12.0 https://yetus.apache.org

This message was automatically generated.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	1m 9s	Docker mode activated.
		_ Prechecks _
+1 💚	dupname	0m 0s	No case conflicting files found.
+1 💚	@author	0m 0s	The patch does not contain any @author tags.
		_ master Compile Tests _
+1 💚	mvninstall	3m 56s	master passed
+0 🆗	refguide	3m 28s	branch has no errors when building the reference guide. See footer for rendered docs, which you should manually inspect.
		_ Patch Compile Tests _
+1 💚	mvninstall	3m 37s	the patch passed
+1 💚	whitespace	0m 0s	The patch has no whitespace issues.
+0 🆗	refguide	3m 25s	patch has no errors when building the reference guide. See footer for rendered docs, which you should manually inspect.
		_ Other Tests _
+1 💚	asflicense	0m 18s	The patch does not generate ASF License warnings.
		17m 29s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/artifact/yetus-general-check/output/Dockerfile
GITHUB PR	#3211
JIRA Issue	HBASE-25816
Optional Tests	dupname asflicense refguide
uname	Linux 4ab5eb7a0d96 4.15.0-65-generic #74-Ubuntu SMP Tue Sep 17 17:06:04 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 6c65314
refguide	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/artifact/yetus-general-check/output/branch-site/book.html
refguide	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/artifact/yetus-general-check/output/patch-site/book.html
Max. process+thread count	78 (vs. ulimit of 30000)
modules	C: . U: .
Console output	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3211/1/console
versions	git=2.17.1 maven=3.6.3
Powered by	Apache Yetus 0.12.0 https://yetus.apache.org

This message was automatically generated.

[Kota-SH]

Hi @jatsakthi @petersomogyi,

Could you please review this PR and provide feedback?

Thanks,
Shanmukha K

[jatsakthi]

+1. Thanks for the fixes, Shanmukha.

[jatsakthi]

Merged.