HDDS-9060. [snapshot] Add unit-testcase for snapshot fs -deleteSnapshot

[jyotirmoy-gh]

What changes were proposed in this pull request?

Add UTs for fs deleteSnapshot - TestOzoneFsSnapshot#testSnapshotDeleteFailure

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-9060

How was this patch tested?

Testcase file - hadoop-ozone/integration-test/src/test/java/org/apache/hadoop/fs/ozone/TestOzoneFsSnapshot.java

mvn -l testlog.out -Dtest=TestOzoneFsSnapshot#testSnapshotDeleteFailure test
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running org.apache.hadoop.fs.ozone.TestOzoneFsSnapshot
[INFO] Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 21.999 s - in org.apache.hadoop.fs.ozone.TestOzoneFsSnapshot
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 4, Failures: 0, Errors: 0, Skipped: 0

[jyotirmoy-gh]

Please review - @nilotpalnandi @sadanand48 @smengcl

[sadanand48]

Thanks @jyotirmoy-gh for the patch. LGTM