csi: add test for rbd ls with rados namespace

[OdedViner]

this pr introduces a new test to verify the rbd ls
command functionality when working with rados namespaces.
the test ensures that rbd images are correctly listed

$ ./bin/kubectl-rook-ceph rbd ls
poolName            imageName                                     namespace    
--------            ---------                                     ---------    
blockpool-rados-ns  csi-vol-465d5545-b621-4adb-afd6-fd548dbd0062  namespace-a  
blockpool-rados-ns  ---                                           namespace-b  
replicapool         ---                                           ---  

when namespaces are configured.

Checklist:

• Commit Message Formatting: Commit titles and messages follow guidelines in the developer guide.
• Reviewed the developer guide on Submitting a Pull Request
• Documentation has been updated, if necessary.
• Unit tests have been added, if necessary.
• Integration tests have been added, if necessary.

[travisn]

Please add a description to the PR and commit message.

[OdedViner]

Please add a description to the PR and commit message.

@travisn done

[subhamkrai]

@OdedViner with this PR you are creating the resources and the test is already in place. Right?

[OdedViner]

@OdedViner with this PR you are creating the resources and the test is already in place. Right?

@subhamkrai Correct, the test runs rbd ls with the rados namespace, both with and without a storage class.