HBASE-25642 Fix or stop warning about already cached block

[apurtell]

Our logs have as a fairly common occurrence: 2021-03-05 22:24:31,034 WARN
[StoreFileOpener-foo-1] hfile.BlockCacheUtil: Caching an already cached
block: blah.bub. This is harmless and can happen in rare cases (see HBASE-8547)

Because it is harmless, log at DEBUG level, not WARN.

[shahrs87]

Do we need LOG. isDebugEnabled condition ?

[apurtell]

@shahrs87 No. In fact I was asked to remove such a guard on another PR. HBase 2+ uses logging libraries that do substitutions on '{}' only if the log level is enabled. So guards are no longer necessary.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	1m 5s	Docker mode activated.
		_ Prechecks _
+1 💚	dupname	0m 0s	No case conflicting files found.
+1 💚	hbaseanti	0m 0s	Patch does not have any anti-patterns.
+1 💚	@author	0m 0s	The patch does not contain any @author tags.
		_ master Compile Tests _
+1 💚	mvninstall	4m 25s	master passed
+1 💚	compile	3m 25s	master passed
+1 💚	checkstyle	1m 11s	master passed
+1 💚	spotbugs	2m 14s	master passed
		_ Patch Compile Tests _
+1 💚	mvninstall	4m 3s	the patch passed
+1 💚	compile	3m 19s	the patch passed
+1 💚	javac	3m 19s	the patch passed
+1 💚	checkstyle	1m 8s	the patch passed
+1 💚	whitespace	0m 0s	The patch has no whitespace issues.
+1 💚	hadoopcheck	20m 20s	Patch does not cause any errors with Hadoop 3.1.2 3.2.1 3.3.0.
+1 💚	spotbugs	2m 24s	the patch passed
		_ Other Tests _
+1 💚	asflicense	0m 13s	The patch does not generate ASF License warnings.
		52m 12s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/artifact/yetus-general-check/output/Dockerfile
GITHUB PR	#3638
Optional Tests	dupname asflicense javac spotbugs hadoopcheck hbaseanti checkstyle compile
uname	Linux 3aa21cb258e8 4.15.0-147-generic #151-Ubuntu SMP Fri Jun 18 19:21:19 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 07c0eee
Default Java	AdoptOpenJDK-1.8.0_282-b08
Max. process+thread count	86 (vs. ulimit of 30000)
modules	C: hbase-server U: hbase-server
Console output	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/console
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[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	1m 2s	Docker mode activated.
-0 ⚠️	yetus	0m 3s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
+1 💚	mvninstall	5m 4s	master passed
+1 💚	compile	1m 18s	master passed
+1 💚	shadedjars	9m 9s	branch has no errors when building our shaded downstream artifacts.
+1 💚	javadoc	0m 43s	master passed
		_ Patch Compile Tests _
+1 💚	mvninstall	4m 55s	the patch passed
+1 💚	compile	1m 19s	the patch passed
+1 💚	javac	1m 19s	the patch passed
+1 💚	shadedjars	9m 9s	patch has no errors when building our shaded downstream artifacts.
+1 💚	javadoc	0m 42s	the patch passed
		_ Other Tests _
+1 💚	unit	205m 43s	hbase-server in the patch passed.
		241m 9s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/artifact/yetus-jdk11-hadoop3-check/output/Dockerfile
GITHUB PR	#3638
Optional Tests	javac javadoc unit shadedjars compile
uname	Linux fdae2dc7a378 4.15.0-147-generic #151-Ubuntu SMP Fri Jun 18 19:21:19 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 07c0eee
Default Java	AdoptOpenJDK-11.0.10+9
Test Results	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/testReport/
Max. process+thread count	3775 (vs. ulimit of 30000)
modules	C: hbase-server U: hbase-server
Console output	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/console
versions	git=2.17.1 maven=3.6.3
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[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	1m 8s	Docker mode activated.
-0 ⚠️	yetus	0m 4s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
+1 💚	mvninstall	4m 25s	master passed
+1 💚	compile	1m 4s	master passed
+1 💚	shadedjars	9m 0s	branch has no errors when building our shaded downstream artifacts.
+1 💚	javadoc	0m 38s	master passed
		_ Patch Compile Tests _
+1 💚	mvninstall	4m 8s	the patch passed
+1 💚	compile	1m 1s	the patch passed
+1 💚	javac	1m 1s	the patch passed
+1 💚	shadedjars	9m 6s	patch has no errors when building our shaded downstream artifacts.
+1 💚	javadoc	0m 37s	the patch passed
		_ Other Tests _
+1 💚	unit	214m 20s	hbase-server in the patch passed.
		247m 29s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/artifact/yetus-jdk8-hadoop3-check/output/Dockerfile
GITHUB PR	#3638
Optional Tests	javac javadoc unit shadedjars compile
uname	Linux e887b4f6116e 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/hbase-personality.sh
git revision	master / 07c0eee
Default Java	AdoptOpenJDK-1.8.0_282-b08
Test Results	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/testReport/
Max. process+thread count	4197 (vs. ulimit of 30000)
modules	C: hbase-server U: hbase-server
Console output	https://ci-hadoop.apache.org/job/HBase/job/HBase-PreCommit-GitHub-PR/job/PR-3638/1/console
versions	git=2.17.1 maven=3.6.3
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