Comment 0 for bug 1942766

def _detach_with_retry(
       if persistent_dev:
            try:
                self._detach_from_persistent(
                    guest, instance_uuid, persistent_dev, get_device_conf_func,
                    device_name)

Because the detach disk first releases the persist xml now, when the live detach the disk timeout, the persist xml is also gone.
If the virtual machine is soft rebooted at this time, the virtual machine will be lost disk because the persistent xml is missing.