HADOOP-17995. Stale record should be remove when DataNodePeerMetrics#dumpSendPacketDownstreamAvgInfoAsJson

[haiyang1987]

Description of PR
As HADOOP-16947 problem with description.
Stale SumAndCount also should be remove when DataNodePeerMetrics#dumpSendPacketDownstreamAvgInfoAsJson.
Ensure the DataNode JMX get SendPacketDownstreamAvgInfo Metrics is accurate.

Details: HADOOP-17995

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 46s		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 appears to include 1 new or modified test files.
			_ trunk Compile Tests _
+0 🆗	mvndep	12m 54s		Maven dependency ordering for branch
+1 💚	mvninstall	24m 43s		trunk passed
+1 💚	compile	26m 23s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	compile	21m 59s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	checkstyle	4m 15s		trunk passed
+1 💚	mvnsite	3m 33s		trunk passed
+1 💚	javadoc	2m 24s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	3m 36s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	6m 43s		trunk passed
+1 💚	shadedclient	24m 38s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+0 🆗	mvndep	0m 31s		Maven dependency ordering for patch
+1 💚	mvninstall	2m 45s		the patch passed
+1 💚	compile	26m 46s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javac	26m 46s		the patch passed
+1 💚	compile	25m 15s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	javac	25m 15s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	4m 11s		the patch passed
+1 💚	mvnsite	4m 17s		the patch passed
+1 💚	javadoc	2m 27s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	3m 41s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	7m 44s		the patch passed
+1 💚	shadedclient	27m 56s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	18m 24s		hadoop-common in the patch passed.
+1 💚	unit	248m 19s		hadoop-hdfs in the patch passed.
+1 💚	asflicense	1m 17s		The patch does not generate ASF License warnings.
		503m 28s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3708/1/artifact/out/Dockerfile
GITHUB PR	#3708
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 2c9b9cd365d6 4.15.0-156-generic #163-Ubuntu SMP Thu Aug 19 23:31:58 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 699d8a7
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-3708/1/testReport/
Max. process+thread count	2906 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common hadoop-hdfs-project/hadoop-hdfs U: .
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3708/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[ferhui]

LGTM

[ferhui]

cc @steveloughran @sodonnel

[sodonnel]

+1 from me. The CI report is green too, so all good there.

[ferhui]

@haiyang1987 Thanks for fixing. @sodonnel Thanks for review!