Description of problem:

error: An error occurred, but the cause is unknown

Version-Release number of selected component (if applicable):
libvirt 5.5.0

How reproducible:
always

Steps to Reproduce:
1. create an rbd raw image on ceph
2. run virsh vol-clone vm_volumes/myfirstimage-root vm_volumes/myfirstimage-root-clone

Actual results:
error: Failed to clone vol from myfirstimage-root
error: An error occurred, but the cause is unknown

Expected results:
that it creates the clone

Additional info:

Equivalent to this, the snapshot features (snapshot-create, snapshot-delete e.g.) also need to function.