Describe the bug
I didn't set a storage class when creating a migration using DVM. I did get a warning, but in this case I would have expected to see the default provisioner used. Instead the storageclass was set to "" on the PVC rather than left off. This does not have the effect of using the Default Provisioner.

Additional context
https://kubernetes.io/docs/concepts/storage/persistent-volumes/#class-1

PVCs don't necessarily have to request a class. A PVC with its storageClassName set equal to "" is always
interpreted to be requesting a PV with no class, so it can only be bound to PVs with no class (no annotation
or one set equal to ""). A PVC with no storageClassName is not quite the same and is treated differently by the
cluster, depending on whether the DefaultStorageClass admission plugin is turned on.

We need to have a "no class" "" option in the drop down for cases like NFS. But we should probably have a (default) option in the drop down that omits setting the storageClassName so the default provisioner is used. Alternatively the user can pick any one of the classes available as is the case now.