[YARN-10545] Improve the readability of diagnostics log in yarn-ui2 web page.

[echohlne]

fix this
https://issues.apache.org/jira/browse/YARN-10545

manual test works well:

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 29s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
			_ trunk Compile Tests _
+1 💚	mvninstall	33m 12s		trunk passed
+1 💚	shadedclient	48m 22s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 13s		the patch passed
+1 💚	whitespace	0m 0s		The patch has no whitespace issues.
+1 💚	shadedclient	14m 53s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	asflicense	0m 31s		The patch does not generate ASF License warnings.
		65m 58s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2540/1/artifact/out/Dockerfile
GITHUB PR	#2540
Optional Tests	dupname asflicense shadedclient
uname	Linux 8256f970f0e3 4.15.0-60-generic #67-Ubuntu SMP Thu Aug 22 16:55:30 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / be35fa1
Max. process+thread count	539 (vs. ulimit of 5500)
modules	C: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-ui U: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-ui
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2540/1/console
versions	git=2.17.1 maven=3.6.0
Powered by	Apache Yetus 0.13.0-SNAPSHOT https://yetus.apache.org

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[echohlne]

@sunilgovind @tangzhankun @jiwq This pr has heen hang for a long time, can you help to review this? thanks a lot....

[jiwq]

Good work! LGTM @zhuqi-lucas

[zhuqi-lucas]

Thanks @Kyoty for patch, @jiwq for review.
LGTM +1.