HBASE-21257 misspelled words.[occured -> occurred]

[gangxueZhang]

This PR is used to replace PR#91. The modification only involves spelling errors in the words in the comments, and does not affect the program function. PR#91 will be closed and the modified content will not be merged into the master branch.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
0	reexec	25	Docker mode activated.
		_ Prechecks _
+1	hbaseanti	0	Patch does not have any anti-patterns.
+1	@author	0	The patch does not contain any @author tags.
+1	test4tests	0	The patch appears to include 1 new or modified test files.
		_ master Compile Tests _
0	mvndep	26	Maven dependency ordering for branch
+1	mvninstall	263	master passed
+1	compile	107	master passed
+1	checkstyle	95	master passed
+1	shadedjars	275	branch has no errors when building our shaded downstream artifacts.
+1	findbugs	231	master passed
+1	javadoc	69	master passed
		_ Patch Compile Tests _
0	mvndep	15	Maven dependency ordering for patch
+1	mvninstall	251	the patch passed
+1	compile	110	the patch passed
+1	javac	110	the patch passed
+1	checkstyle	98	the patch passed
+1	whitespace	0	The patch has no whitespace issues.
+1	shadedjars	280	patch has no errors when building our shaded downstream artifacts.
+1	hadoopcheck	527	Patch does not cause any errors with Hadoop 2.7.4 or 3.0.0.
+1	findbugs	250	the patch passed
+1	javadoc	65	the patch passed
		_ Other Tests _
+1	unit	8840	hbase-server in the patch passed.
+1	unit	70	hbase-it in the patch passed.
+1	unit	260	hbase-rest in the patch passed.
+1	asflicense	88	The patch does not generate ASF License warnings.
		12045

Subsystem	Report/Notes
Docker	Client=17.05.0-ce Server=17.05.0-ce base: https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-146/1/artifact/out/Dockerfile
GITHUB PR	#146
Optional Tests	dupname asflicense javac javadoc unit findbugs shadedjars hadoopcheck hbaseanti checkstyle compile
uname	Linux 6eb425996922 4.4.0-139-generic #165-Ubuntu SMP Wed Oct 24 10:58:50 UTC 2018 x86_64 GNU/Linux
Build tool	maven
Personality	/testptch/patchprocess/precommit/personality/provided.sh
git revision	master / 16146a1
maven	version: Apache Maven 3.5.4 (1edded0938998edf8bf061f1ceb3cfdeccf443fe; 2018-06-17T18:33:14Z)
Default Java	1.8.0_181
findbugs	v3.1.11
Test Results	https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-146/1/testReport/
Max. process+thread count	4922 (vs. ulimit of 10000)
modules	C: hbase-server hbase-it hbase-rest U: .
Console output	https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-146/1/console
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