Enhance Integration Test to cover all special cases of cascade delete of resources for VM deletion.

[elankath]

How to categorize this issue?

/area testing
/kind enhancement
/priority 3

What would you like to be added:
We had a bug in the DeleteMachine implementation in Azure where cascade delete option was set for all resources attached to the VM. It should be set only for the resources that were created as a part of VM creation. Ideally, an Integration Test should have caught this.

Why is this needed:
See gardener/machine-controller-manager-provider-azure#142

[rishabh-11]

On thinking more about this, we have another problem here. The IT that we have are not provider-specific. It makes it very difficult to add a test for this case

[elankath]

We just need an extension of the Driver interface say DriverTest that provides an additional methods we want for IT's.