Currently, attempts to use local-attach with the newest
attachment API microversion, 3.44, results in the attchment
hanging at 'attaching'. This is because brick-cinderclient-ext
was not updated to use the 'attachment.complete(attachment_id)
step when attaching.
This adds this call so that the attachment will complete.
Change-Id: I19983e3e38771da87b8471673a15daf59dc5f25f
closes-bug: 1739653