We need to cope with 0 or more '0' prefixed to '$dev':
# stat -c '%D' "/system.img"
13
# losetup -a
/dev/loop0: [0013]:12062248 (/system.img)
Signed-off-by: Zhigang Wang <zhigang.x.wang@oracle.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>