Fix unit tests

[atye]

PR Submission checklist

Fix Client unit tests by using api.ContextKey type.

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#1091

Common PR Checklist:

• Have you made sure that the code compiles?
• Have you commented your code, particularly in hard-to-understand areas
• Did you run tests in a real Kubernetes cluster?
• Have you maintained backward compatibility

Description of your changes:

Use api.ContextKey type.

[delldubey]

lgtm