Helm installation changes for csi-unity

[karthikk92]

Description

Helm installation changes for csi-unity

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#877

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?

Tested for

1. Using csi-install.sh scripts
2. Using csi-offline bundle installation scripts.

Note: Added support for v2.7.0 driver versions . Updating to the v2.8.0 is in progress , since we need to decide which tag to be cloned from helm chart. So will raise separate pr for bumping up the version to v2.8.0.