MAPREDUCE-7360. Clean shared state pollution to avoid flaky tests

[LALAYANG]

Link to issue: https://issues.apache.org/jira/browse/MAPREDUCE-7360

What is the purpose of this change

This PR is to clean shared state pollution between tests:

Test1: org.apache.hadoop.mapreduce.v2.app.TestJobEndNotifier.testNotificationOnLastRetryShutdownWithRuntimeException
Test2: org.apache.hadoop.mapreduce.v2.app.TestMRAppMaster.testMRAppMasterShutDownJob

• Test1 can pollute the shared state with Test2, which can lead Test2 to fail after running Test1.
• It may be better to clean state pollutions so that some other tests won't fail in the future due to the shared state polluted by this test.

Reproduce test failure

First run Test1, then run Test2 in the same JVM

Expected result

The tests should run successfully when multiple tests that use this state are run in the same JVM.

Actual result

Run Test1 and Test2, Test2 fails:

[ERROR]   TestMRAppMaster.testMRAppMasterShutDownJob:530 Expected shutDownJob to exit with status code of 0. expected:<0> but was:<1>

Fix

Reset FirstExitException at the start of Test2 to clean the pollution from Test1.

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	1m 29s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+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.
			_ trunk Compile Tests _
+1 💚	mvninstall	32m 29s		trunk passed
+1 💚	compile	0m 38s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	compile	0m 30s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	checkstyle	0m 26s		trunk passed
+1 💚	mvnsite	0m 37s		trunk passed
+1 💚	javadoc	0m 30s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	0m 27s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	1m 0s		trunk passed
+1 💚	shadedclient	16m 43s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 33s		the patch passed
+1 💚	compile	0m 30s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javac	0m 30s		the patch passed
+1 💚	compile	0m 25s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	javac	0m 25s		the patch passed
+1 💚	blanks	0m 1s		The patch has no blanks issues.
+1 💚	checkstyle	0m 20s		the patch passed
+1 💚	mvnsite	0m 29s		the patch passed
+1 💚	javadoc	0m 22s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	0m 20s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	1m 4s		the patch passed
+1 💚	shadedclient	16m 47s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	8m 16s		hadoop-mapreduce-client-app in the patch passed.
+1 💚	asflicense	0m 32s		The patch does not generate ASF License warnings.
		85m 42s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3300/1/artifact/out/Dockerfile
GITHUB PR	#3300
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 592299e4a473 4.15.0-143-generic #147-Ubuntu SMP Wed Apr 14 16:10:11 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / fa33fdb
Default Java	Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3300/1/testReport/
Max. process+thread count	573 (vs. ulimit of 5500)
modules	C: hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app U: hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3300/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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