HDFS-16149.Improve the parameter annotation in FairCallQueue#priorityLevels.

[jianghuazhu]

…Levels.

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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
the corresponding JIRA issue number. (e.g. HADOOP-XXXXX. Fix a typo in YYY.)
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[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 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	35m 19s		trunk passed
+1 💚	compile	27m 26s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	compile	21m 37s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	checkstyle	1m 2s		trunk passed
+1 💚	mvnsite	1m 32s		trunk passed
+1 💚	javadoc	1m 1s		trunk passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	1m 34s		trunk passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	2m 29s		trunk passed
+1 💚	shadedclient	21m 44s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 20s		the patch passed
+1 💚	compile	37m 43s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javac	37m 43s		the patch passed
+1 💚	compile	35m 45s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	javac	35m 45s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	2m 5s		the patch passed
+1 💚	mvnsite	3m 11s		the patch passed
+1 💚	javadoc	1m 55s		the patch passed with JDK Ubuntu-11.0.11+9-Ubuntu-0ubuntu2.20.04
+1 💚	javadoc	2m 37s		the patch passed with JDK Private Build-1.8.0_292-8u292-b10-0ubuntu1~20.04-b10
+1 💚	spotbugs	4m 37s		the patch passed
+1 💚	shadedclient	27m 23s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	21m 8s	/patch-unit-hadoop-common-project_hadoop-common.txt	hadoop-common in the patch passed.
-1 ❌	asflicense	1m 17s	/results-asflicense.txt	The patch generated 4 ASF License warnings.
		254m 30s

Reason	Tests
Failed junit tests	hadoop.metrics2.lib.TestMutableMetrics
	hadoop.ipc.TestCallQueueManager
	hadoop.metrics2.source.TestJvmMetrics

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3255/1/artifact/out/Dockerfile
GITHUB PR	#3255
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 60fb3c3ef4f2 4.15.0-142-generic #146-Ubuntu SMP Tue Apr 13 01:11:19 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 164a65a
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-3255/1/testReport/
Max. process+thread count	2515 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common U: hadoop-common-project/hadoop-common
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-3255/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[jianghuazhu]

Some exceptions occurred in UT:
1.Missing Apache License;
2.java.lang.OutOfMemoryError;
But it seems that these phenomena are not highly related to the code I submitted;

[jojochuang]

+1 will merge shortly.