[test] add more CI tests for blobfuse and smb flexvol plugins

**Is your feature request related to a problem? Please describe.**

Current CI tests for blobfuse and smb flexvol plugins are not enough, need to at least add mount/unmount tests
https://github.com/Azure/kubernetes-volume-drivers/blob/34de2a1d7eec0fcdcd0342fd99950cb3dbadf0d5/flexvolume/blobfuse/test/run-test.sh#L16

**Describe the solution you'd like in detail**

**Describe alternatives you've considered**

**Additional context**

Start with flexvolume/blobfuse/test/run-test.sh at the referenced line and inspect the existing CI test flow for the blobfuse and smb flexvol plugins. Add coverage for mount and unmount operations, then run the relevant CI test entry point and confirm both plugins pass those checks.

Written by the indexing model from the issue text.