Resolving SR Not Unpluggable After NBD Backup Errors

a573

I noticed that sr could not unplug after the NBD backup failed.

I'll blurt out the solution. There may be others out there, but I hope it helps someone.
I assume this is because when an NBD backup makes a vbd connection and exits with an error, the vbd connection is not broken.

# xe pbd-unplug uuid=79a53996-60d7-8fc0-1f8b-ba1e30b5d0ce
This operation cannot be performed because this VDI is in use by some other operation
vdi: 41b7ff1a-05be-43db-a592-849f9ab30444 (***************)
operation: 071e6f0b-9670-44b6-b455-b8d1319da28b (***************)

# xe vdi-param-list uuid=071e6f0b-9670-44b6-b455-b8d1319da28b | grep vbd-uuids
               vbd-uuids (SRO): 61a50e07-51c4-3476-d47c-45e756f127fe

Unplug the displayed vbd-uuids.

# xe vbd-unplug uuid=61a50e07-51c4-3476-d47c-45e756f127fe