Remove duplicated line from _do_attachment_delete
Remove duplicated line from _do_attachment_delete

Change-Id: I56a9ec4ee9ded4917546f86ea7f0090ab4a3223b

mahak/cinder,openstack/cinder,eharney/cinder,openstack/cinder,eharney/cinder,mahak/cinder,phenoxim/cinder,Datera/cinder,Datera/cinder,j-griffith/cinder,j-griffith/cinder,phenoxim/cinder