Fix volume attachment event parsing and KeyError on volume create/delete

The correct name of the server-identifying field in volume attach/detach
notification is `instance_uud`, not `server_id`, see
`cinder/objects/volume_attachment.py`

Cinder changed format of notifications in rocky,
as image_id in glance_metadata is not a list anymore

Related-Issue: PROD-35592
Change-Id: Idbeacd134afd01484f8098513a16e625de35b014
1 file changed