qemu_img_info: report 'luks' images as 'raw'
qemu_img_info: report 'luks' images as 'raw'

qemu-img info will report luks-formatted images as
file format 'luks', but from Cinder's point of view,
these are just raw images.  We do not treat LUKS as
a separate format and can use tools like 'dd' to move
data from luks-formatted images.

Change-Id: Ib4f03cb3a8490a36396fd61e396980650f0a536f

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