It was broken by 
efaa7c4eeb7 when it dropped the device name "image"
from BB API.  Now this error message text is updated again, sync it up.
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 
20170119130759.28319-3-famz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
 0x140000000     0x10000         0x50000         TEST_DIR/iotest-version3-s003.vmdk
 
 === Testing afl image with a very large capacity ===
-qemu-img: Can't get size of device 'image': File too large
+qemu-img: Can't get image size 'TEST_DIR/afl9.IMGFMT': File too large
 *** done