Update documentation:

Propose to update the documentation for CNV 4.16, 4.17 and 4.18 regarding StorageProfiles with the following:

We should indicate that:
If the storageclass of the volume has a storageprofile configured with snapshotclass then that will be the volumesnapshotclass chosen for the vmsnapshot of that volume.
 
If no such definition exists the volumesnapshotclass for the volume storageclass will be chosen.

If more then one exists then it has to have the default annotation or else an error will be returned.