CAT-1912 : Adding new getters and setters for stripes & not allowing change of stripes for an existing lvm

[malikparvez]

Summary

Adding new getters and setters for stripes.

Additional Context

Add any additional context about the problem here.

• [ ] Root cause and the steps to reproduce. (If applicable)
• [ ] Thought process behind the implementation.

Related Issues (if any)

Mention any related issues or pull requests.

Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [ ] Manually verified. (For example puppet apply)