HDDS-1941. Unused executor in SimpleContainerDownloader

[adoroszlai]

What changes were proposed in this pull request?

Remove unused executor from SimpleContainerDownloader.

https://issues.apache.org/jira/browse/HDDS-1941

[adoroszlai]

/label ozone

[bharatviswa504]

+1 LGTM.

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Comment
0	reexec	93	Docker mode activated.
		_ Prechecks _
+1	dupname	0	No case conflicting files found.
+1	@author	0	The patch does not contain any @author tags.
-1	test4tests	0	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	633	trunk passed
+1	compile	378	trunk passed
+1	checkstyle	75	trunk passed
+1	mvnsite	0	trunk passed
+1	shadedclient	951	branch has no errors when building and testing our client artifacts.
+1	javadoc	188	trunk passed
0	spotbugs	455	Used deprecated FindBugs config; considering switching to SpotBugs.
+1	findbugs	682	trunk passed
		_ Patch Compile Tests _
+1	mvninstall	561	the patch passed
+1	compile	392	the patch passed
+1	javac	392	the patch passed
+1	checkstyle	78	the patch passed
+1	mvnsite	0	the patch passed
+1	whitespace	0	The patch has no whitespace issues.
+1	shadedclient	864	patch has no errors when building and testing our client artifacts.
+1	javadoc	202	the patch passed
+1	findbugs	833	the patch passed
		_ Other Tests _
+1	unit	430	hadoop-hdds in the patch passed.
-1	unit	2536	hadoop-ozone in the patch failed.
+1	asflicense	62	The patch does not generate ASF License warnings.
		9121

Reason	Tests
Failed junit tests	hadoop.ozone.client.rpc.TestBlockOutputStream
	hadoop.ozone.client.rpc.TestHybridPipelineOnDatanode
	hadoop.ozone.TestStorageContainerManager
	hadoop.ozone.client.rpc.TestOzoneClientRetriesOnException
	hadoop.ozone.client.rpc.Test2WayCommitInRatis

Subsystem	Report/Notes
Docker	Client=19.03.1 Server=19.03.1 base: https://builds.apache.org/job/hadoop-multibranch/job/PR-1367/1/artifact/out/Dockerfile
GITHUB PR	#1367
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient findbugs checkstyle
uname	Linux 58e11bd4bfce 4.15.0-54-generic #58-Ubuntu SMP Mon Jun 24 10:55:24 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	personality/hadoop.sh
git revision	trunk / aef6a4f
Default Java	1.8.0_222
unit	https://builds.apache.org/job/hadoop-multibranch/job/PR-1367/1/artifact/out/patch-unit-hadoop-ozone.txt
Test Results	https://builds.apache.org/job/hadoop-multibranch/job/PR-1367/1/testReport/
Max. process+thread count	3965 (vs. ulimit of 5500)
modules	C: hadoop-hdds/container-service U: hadoop-hdds/container-service
Console output	https://builds.apache.org/job/hadoop-multibranch/job/PR-1367/1/console
versions	git=2.7.4 maven=3.3.9 findbugs=3.1.0-RC1
Powered by	Apache Yetus 0.10.0 http://yetus.apache.org

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[bharatviswa504]

Thank You @adoroszlai for the contribution.
Test failures are not related to this patch. I will commit this to the trunk.

[adoroszlai]

Thanks @bharatviswa504 for reviewing and committing it.