[nova] patch delete dangling bdms lead to VM Error

Hi community,

I've got the error with this patch while rebooting VM with volume source from the image, the result VM state is Error with the message "VolumeDeviceNotFound" (Tested with Netapp & PowerStrore iSCSI SAN driver)

Please take a look at this! https://review.opendev.org/c/openstack/nova/+/882284