qemu-iotests: 082: Filter the real disk size The real on-disk size of an image depends on things like the host filesystem. _img_info already filters it out, use the function in 082. Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>