HDFS-16385. Fix Datanode retrieve slownode information bug.

[Jackson-Wang-7]

Description of PR

in HDFS-16320, the DataNode will retrieve the SLOW status from each NameNode. But it didn't set isSlowNode to HeartbeatResponseProto in DatanodeProtocolServerSideTranslatorPB#sendHeartbeat.

How was this patch tested?

I constructed some slownode scenarios to test getting the slownode results correctly.

For code changes:

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 51s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 1s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+1 💚	mvninstall	34m 8s		trunk passed
+1 💚	compile	1m 40s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	compile	1m 33s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	checkstyle	1m 9s		trunk passed
+1 💚	mvnsite	1m 38s		trunk passed
+1 💚	javadoc	1m 12s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	1m 47s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	4m 18s		trunk passed
+1 💚	shadedclient	30m 26s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 45s		the patch passed
+1 💚	compile	1m 54s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javac	1m 54s		the patch passed
+1 💚	compile	1m 26s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	javac	1m 26s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 52s		the patch passed
+1 💚	mvnsite	1m 21s		the patch passed
+1 💚	javadoc	0m 52s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	1m 27s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	3m 18s		the patch passed
+1 💚	shadedclient	22m 43s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	32m 8s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+0 🆗	asflicense	0m 27s		ASF License check generated no output?
		144m 7s

Reason	Tests
Failed junit tests	hadoop.hdfs.server.datanode.fsdataset.impl.TestLazyPersistLockedMemory
	hadoop.metrics2.sink.TestRollingFileSystemSinkWithHdfs
	hadoop.hdfs.server.datanode.fsdataset.impl.TestLazyPersistFiles
	hadoop.hdfs.server.datanode.TestBlockScanner
	hadoop.metrics2.sink.TestRollingFileSystemSinkWithSecureHdfs
	hadoop.hdfs.server.datanode.fsdataset.impl.TestSpaceReservation

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3803/1/artifact/out/Dockerfile
GITHUB PR	#3803
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 7bf77c3965b3 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/bin/hadoop.sh
git revision	trunk / fd35e5a
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-3803/1/testReport/
Max. process+thread count	717 (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-3803/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[ferhui]

@symious Can you please take a look?

[symious]

LGTM. Thanks for spotting the bug.

[tasanuma]

Thanks for fixing the issue, @Jackson-Wang-7. Thanks for your reviews, @symious, @ferhui, @tomscut.