HADOOP-17138. Fix spotbugs warnings surfaced after upgrade to 4.0.6. …

[aajisaka]

…(#2155)

(cherry picked from commit 1b29c9b)

Backport HADOOP-17138 to branch-3.3 to fix the findbugs warnings in hadoop-cos.

[aajisaka]

I created a PR for running the unit tests in branch-3.3. If the result is fine, I'll cherry-pick it to branch-3.3.

[sunchao]

LGTM on pending CI - thanks @aajisaka

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	32m 16s	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 💚	test4tests	0m 0s	The patch appears to include 1 new or modified test files.
		_ branch-3.3 Compile Tests _
+0 🆗	mvndep	3m 52s	Maven dependency ordering for branch
+1 💚	mvninstall	33m 47s	branch-3.3 passed
+1 💚	compile	23m 9s	branch-3.3 passed
+1 💚	checkstyle	3m 38s	branch-3.3 passed
+1 💚	mvnsite	13m 59s	branch-3.3 passed
+1 💚	shadedclient	38m 36s	branch has no errors when building and testing our client artifacts.
+1 💚	javadoc	6m 49s	branch-3.3 passed
+0 🆗	spotbugs	0m 54s	Used deprecated FindBugs config; considering switching to SpotBugs.
-1 ❌	findbugs	15m 5s	hadoop-yarn-project/hadoop-yarn in branch-3.3 has 2 extant findbugs warnings.
-1 ❌	findbugs	0m 43s	hadoop-cloud-storage-project/hadoop-cos in branch-3.3 has 1 extant findbugs warnings.
-1 ❌	findbugs	0m 53s	hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase-tests in branch-3.3 has 2 extant findbugs warnings.
		_ Patch Compile Tests _
+0 🆗	mvndep	0m 26s	Maven dependency ordering for patch
+1 💚	mvninstall	12m 2s	the patch passed
+1 💚	compile	19m 43s	the patch passed
+1 💚	javac	19m 43s	the patch passed
+1 💚	checkstyle	2m 58s	the patch passed
+1 💚	mvnsite	12m 35s	the patch passed
+1 💚	whitespace	0m 0s	The patch has no whitespace issues.
+1 💚	xml	0m 4s	The patch has no ill-formed XML file.
+1 💚	shadedclient	16m 57s	patch has no errors when building and testing our client artifacts.
+1 💚	javadoc	5m 37s	the patch passed
+1 💚	findbugs	2m 17s	hadoop-common in the patch passed.
+1 💚	findbugs	3m 29s	hadoop-hdfs in the patch passed.
+1 💚	findbugs	13m 18s	hadoop-yarn-project/hadoop-yarn generated 0 new + 0 unchanged - 2 fixed = 0 total (was 2)
+1 💚	findbugs	0m 51s	hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase-tests generated 0 new + 0 unchanged - 2 fixed = 0 total (was 2)
+1 💚	findbugs	4m 17s	hadoop-mapreduce-project in the patch passed.
+1 💚	findbugs	0m 54s	hadoop-sls in the patch passed.
+1 💚	findbugs	0m 42s	hadoop-cloud-storage-project/hadoop-cos generated 0 new + 0 unchanged - 1 fixed = 0 total (was 1)
		_ Other Tests _
-1 ❌	unit	9m 58s	hadoop-common in the patch passed.
-1 ❌	unit	116m 11s	hadoop-hdfs in the patch passed.
-1 ❌	unit	223m 21s	hadoop-yarn in the patch passed.
+1 💚	unit	15m 57s	hadoop-yarn-server-timelineservice-hbase-tests in the patch passed.
+1 💚	unit	152m 59s	hadoop-mapreduce-project in the patch passed.
-1 ❌	unit	12m 40s	hadoop-sls in the patch passed.
+1 💚	unit	0m 45s	hadoop-cos in the patch passed.
+1 💚	asflicense	1m 10s	The patch does not generate ASF License warnings.
		802m 1s

Reason	Tests
Failed junit tests	hadoop.fs.ftp.TestFTPFileSystem
	hadoop.hdfs.TestDecommissionWithStripedBackoffMonitor
	hadoop.hdfs.server.datanode.TestBPOfferService
	hadoop.hdfs.TestDistributedFileSystem
	hadoop.hdfs.server.datanode.TestNNHandlesCombinedBlockReport
	hadoop.yarn.applications.distributedshell.TestDistributedShell
	hadoop.yarn.client.api.impl.TestAMRMClient
	hadoop.yarn.server.resourcemanager.TestRMHATimelineCollectors
	hadoop.yarn.server.resourcemanager.security.TestDelegationTokenRenewer
	hadoop.yarn.server.resourcemanager.scheduler.fair.TestFairSchedulerPreemption
	hadoop.yarn.sls.appmaster.TestAMSimulator

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/Dockerfile
GITHUB PR	#2538
Optional Tests	dupname asflicense xml compile javac javadoc mvninstall mvnsite unit shadedclient findbugs checkstyle
uname	Linux eb91fce54196 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	branch-3.3 / e4cab4b
Default Java	Private Build-1.8.0_275-8u275-b01-0ubuntu1~16.04-b01
findbugs	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/branch-findbugs-hadoop-yarn-project_hadoop-yarn-warnings.html
findbugs	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/branch-findbugs-hadoop-cloud-storage-project_hadoop-cos-warnings.html
findbugs	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/branch-findbugs-hadoop-yarn-project_hadoop-yarn_hadoop-yarn-server_hadoop-yarn-server-timelineservice-hbase-tests-warnings.html
unit	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/patch-unit-hadoop-common-project_hadoop-common.txt
unit	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt
unit	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/patch-unit-hadoop-yarn-project_hadoop-yarn.txt
unit	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/artifact/out/patch-unit-hadoop-tools_hadoop-sls.txt
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/testReport/
Max. process+thread count	3243 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common hadoop-hdfs-project/hadoop-hdfs hadoop-yarn-project/hadoop-yarn hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase-tests hadoop-mapreduce-project hadoop-tools/hadoop-sls hadoop-cloud-storage-project/hadoop-cos U: .
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2538/1/console
versions	git=2.7.4 maven=3.3.9 findbugs=3.1.0-RC1
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[aajisaka]

Merged. Thank you @sunchao for your review.