HDFS-17830. Fix failing TestZKDelegationTokenSecretManagerImpl due to static Curator reuse.

[zhtttylz]

Description of PR

HDFS-17830. Fix failing TestZKDelegationTokenSecretManagerImpl due to static Curator reuse.

TestZKDelegationTokenSecretManagerImpl tests fail with “Expected state [STARTED] was [STOPPED]” due to static Curator reuse

IllegalStateException: Expected state [STARTED] was [STOPPED]
  at CuratorFrameworkImpl.checkState / usingNamespace
  at ZKDelegationTokenSecretManager.<init>(...)

CI evidence:
https://ci-hadoop.apache.org/job/hadoop-qbt-trunk-java8-linux-x86_64/2051/artifact/out/patch-unit-hadoop-hdfs-project_hadoop-hdfs-rbf.txt

Under JUnit 5’s PER_METHOD lifecycle, static fields persist; this suite shares a static CuratorFramework that some tests close without resetting, so later tests reuse a STOPPED client and fail in ZKDelegationTokenSecretManagerImpl (“Expected [STARTED] was [STOPPED]”). It’s an isolation/cleanup issue, not a Curator change—reset or recreate the static client between tests (in @AfterEach).

How was this patch tested?

CI Test.

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	21m 29s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 1s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets 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	55m 28s		trunk passed
+1 💚	compile	1m 16s		trunk passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	compile	0m 43s		trunk passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	checkstyle	0m 33s		trunk passed
+1 💚	mvnsite	0m 48s		trunk passed
+1 💚	javadoc	0m 44s		trunk passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	0m 33s		trunk passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	spotbugs	1m 34s		trunk passed
+1 💚	shadedclient	42m 2s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 36s		the patch passed
+1 💚	compile	1m 5s		the patch passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javac	1m 5s		the patch passed
+1 💚	compile	0m 35s		the patch passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	javac	0m 35s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 20s		the patch passed
+1 💚	mvnsite	0m 38s		the patch passed
+1 💚	javadoc	0m 32s		the patch passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	0m 25s		the patch passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	spotbugs	1m 30s		the patch passed
+1 💚	shadedclient	41m 55s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	53m 35s		hadoop-hdfs-rbf in the patch passed.
+1 💚	asflicense	0m 41s		The patch does not generate ASF License warnings.
		228m 59s

Subsystem	Report/Notes
Docker	ClientAPI=1.51 ServerAPI=1.51 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7960/1/artifact/out/Dockerfile
GITHUB PR	#7960
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux 01ed129e7fec 5.15.0-151-generic #161-Ubuntu SMP Tue Jul 22 14:25:40 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / d961115
Default Java	Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7960/1/testReport/
Max. process+thread count	3608 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs-rbf U: hadoop-hdfs-project/hadoop-hdfs-rbf
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7960/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[slfan1989]

LGTM.

[slfan1989]

@zhtttylz Thanks for the contribution! Merged into trunk.

[zhtttylz]

Thanks @slfan1989 help review and merged!