Fix Log parameter
Fix Log parameter

instance_id is easy to misunderstand as VM ID, and it
doesn't agree with reality,and i think It's better to
log attachment id.

Change-Id: I22481731cacf7c4793e43713291f4c25c1e5afbb

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