Improve code coverage

[lukeatdell]

Description

Refactoring the mock server to address data races around accessing the global struct of "Induced errors".

Unit tests executed by csi-powermax have a dependency on the mock PowerMax server in mock.go. This server handles requests made by csi-powermax code when executing its unit tests. In order to induce errors, there is a global set of boolean vars within the mock server that is set by csi-powermax unit test code, and also read by the running server, leading to data races.

To resolve this, functions that read or otherwise modify the global vars have been unexported, and associated exported functions with the same name and func signature will call these unexported funcs, making sure to acquire the lock first. If necessary, unexported funcs should only call other unexported funcs to avoid deadlock.

Increasing unit test coverage.

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#1747

Checklist:

• Have you run format,vet & lint checks against your submission?
• Have you made sure that the code compiles?
• Did you run the unit & integration tests successfully?
• Have you maintained at least 90% code coverage?
• Have you commented your code, particularly in hard-to-understand areas
• Have you done corresponding changes to the documentation
• Did you run tests in a real Kubernetes cluster?
• Have you maintained at least 90% code coverage?
• 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