Fixed the --attr format for Ephemeral test suite

[adarsh-dell]

Description

Fixed the arg --attr format for ephemeral test suite to keep args format same for both functional and performance suite.

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#930

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
• I have maintained backward compatibility

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

• Run ephemeral test suite by passing fileName as a value to the --attr args and the suites passes as per the expectation.
  ./cert-csi test ephemeral-volume --driver csi-powerstore.dellem c.com --fs-type ext4 --attr attr-file --pods 5 --pod-name wrephe
  

[AkshaySainiDell]

lgtm