HADOOP-18238.Fix reentrancy check in SFTPFileSystem.close()

[hotcodemacha]

Description of PR

Fix reentrancy check in SFTPFileSystem.close()

• JIRA: HADOOP-18238

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 48s		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	40m 48s		trunk passed
+1 💚	compile	26m 30s		trunk passed with JDK Private Build-11.0.15+10-Ubuntu-0ubuntu0.20.04.1
+1 💚	compile	20m 22s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	checkstyle	1m 13s		trunk passed
+1 💚	mvnsite	1m 40s		trunk passed
+1 💚	javadoc	1m 15s		trunk passed with JDK Private Build-11.0.15+10-Ubuntu-0ubuntu0.20.04.1
+1 💚	javadoc	0m 50s		trunk passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	2m 40s		trunk passed
+1 💚	shadedclient	21m 51s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 58s		the patch passed
+1 💚	compile	22m 3s		the patch passed with JDK Private Build-11.0.15+10-Ubuntu-0ubuntu0.20.04.1
+1 💚	javac	22m 3s		the patch passed
+1 💚	compile	19m 50s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	javac	19m 51s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	1m 7s		the patch passed
+1 💚	mvnsite	1m 36s		the patch passed
+1 💚	javadoc	1m 6s		the patch passed with JDK Private Build-11.0.15+10-Ubuntu-0ubuntu0.20.04.1
+1 💚	javadoc	0m 51s		the patch passed with JDK Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	2m 37s		the patch passed
+1 💚	shadedclient	21m 45s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	17m 47s		hadoop-common in the patch passed.
+1 💚	asflicense	1m 3s		The patch does not generate ASF License warnings.
		209m 8s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4330/1/artifact/out/Dockerfile
GITHUB PR	#4330
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux a8bd76dcdbcf 4.15.0-169-generic #177-Ubuntu SMP Thu Feb 3 10:50:38 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / a65cfad
Default Java	Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Private Build-11.0.15+10-Ubuntu-0ubuntu0.20.04.1 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_312-8u312-b07-0ubuntu1~20.04-b07
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4330/1/testReport/
Max. process+thread count	2424 (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-4330/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[dannycjones]

Looks good, I clarified understanding in the comment on HADOOP-18238.

[steveloughran]

+1. merging