Fixed independent deletion of RO snapshot and UT

[shefali-malhotra]

Description

• Added access zone in snapshot handler to access the zone name while deletion of snapshot.
• FIxed UT test cases

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#487

Checklist:

• I have performed a self-review of my own code to ensure there are no formatting, vetting, linting, or security issues
• I have verified that new and existing unit tests pass locally with my changes
• I have not allowed coverage numbers to degenerate
• I have maintained at least 90% code coverage
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Backward compatibility is not broken

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• Ran Unit Test cases

• Validated independent deletion of RO snapshot and volume.

[meggm]

LGTM

[rajkumar-palani]

lgtm