Add Unit Tests for ListVolumes API

[nearora-msft]

Is your feature request related to a problem?/Why is this needed
Implement Unit Tests for ListVolumes API

Describe the solution you'd like in detail
The TestListVolumes UT in the controllerserver_test.go file is skipped for now as it is dependent on some changes in the legacy-cloud-provider.(kubernetes/kubernetes#97341) Make the code changes for the UT once the dependency are available.

Describe alternatives you've considered

Additional context
Related to issue : #378

[nearora-msft]

/assign