HDFS-15703. Don't generate edits for set operations that are no-op

[amahussein]

NOTICE

Please create an issue in ASF JIRA before opening a pull request,
and you need to set the title of the pull request which starts with
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[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	1m 10s		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.
+1 💚		0m 0s	test4tests	The patch appears to include 1 new or modified test files.
			_ trunk Compile Tests _
+1 💚	mvninstall	35m 11s		trunk passed
+1 💚	compile	1m 20s		trunk passed with JDK Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04
+1 💚	compile	1m 13s		trunk passed with JDK Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01
+1 💚	checkstyle	0m 48s		trunk passed
+1 💚	mvnsite	1m 20s		trunk passed
+1 💚	shadedclient	19m 21s		branch has no errors when building and testing our client artifacts.
+1 💚	javadoc	0m 53s		trunk passed with JDK Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04
+1 💚	javadoc	1m 31s		trunk passed with JDK Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01
+0 🆗	spotbugs	3m 29s		Used deprecated FindBugs config; considering switching to SpotBugs.
+1 💚	findbugs	3m 26s		trunk passed
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 16s		the patch passed
+1 💚	compile	1m 24s		the patch passed with JDK Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04
+1 💚	javac	1m 24s		the patch passed
+1 💚	compile	1m 11s		the patch passed with JDK Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01
+1 💚	javac	1m 11s		the patch passed
+1 💚	checkstyle	0m 42s		hadoop-hdfs-project/hadoop-hdfs: The patch generated 0 new + 2 unchanged - 1 fixed = 2 total (was 3)
+1 💚	mvnsite	1m 21s		the patch passed
+1 💚	whitespace	0m 0s		The patch has no whitespace issues.
+1 💚	shadedclient	16m 43s		patch has no errors when building and testing our client artifacts.
+1 💚	javadoc	0m 49s		the patch passed with JDK Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04
+1 💚	javadoc	1m 21s		the patch passed with JDK Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01
+1 💚	findbugs	3m 14s		the patch passed
			_ Other Tests _
-1 ❌	unit	115m 21s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 35s		The patch does not generate ASF License warnings.
		212m 9s

Reason	Tests
Failed junit tests	hadoop.hdfs.TestPread
	hadoop.hdfs.TestDFSClientRetries

Subsystem	Report/Notes
Docker	ClientAPI=1.40 ServerAPI=1.40 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2508/1/artifact/out/Dockerfile
GITHUB PR	#2508
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient findbugs checkstyle
uname	Linux 035de6b61bbd 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 6a1d7d9
Default Java	Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2508/1/testReport/
Max. process+thread count	2758 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2508/1/console
versions	git=2.17.1 maven=3.6.0 findbugs=4.0.6
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[amahussein]

I have checked the failing test case. They are irrelevant.

[jbrennan333]

+1 this looks good. I also verified that the unit tests TestPread and TestDFSClientRetries did not fail for me with this patch.