Comment 1 for bug 1750666

It should be noted that this was found during backporting of https://review.openstack.org/#/c/545132/ to stable/pike where we don't have this code to set the bdm.attachment_id:

https://github.com/openstack/nova/blob/stable/queens/nova/compute/api.py#L3765

This is also a problem for rocky/queens if there are older computes in the deployment.

So the delete code path needs to handle the case that the bdm in the build request doesn't have an attachment_id field set and ignore it, like:

if 'attachment_id' in bdm and bdm.attachment_id:
    volume_api.delete_attachment(...)
else:
    # do the old volume cleanup thing