flock: Don't assume device maj/min numbers are byte long

Igor reported the following file lock

 | (00.003139) lockinfo: 4:POSIX ADVISORY WRITE 46567 b6:5f0b1:524702 0 EOF
 | (00.003154) lockinfo: 5:POSIX ADVISORY WRITE 46559 b6:5f0b1:524661 0 EOF
 | (00.003172) lockinfo: 6:POSIX ADVISORY WRITE 46543 b6:5f0b1:524326 0 0
 | (00.003188) lockinfo: 7:POSIX ADVISORY WRITE 46543 b6:5f0b1:524367 0 EOF

where device maj number is pretty big and parsing failed.
Fix it removing field width.

Reported-by: Igor Sukhih <igor@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>