fix valgrind errors of uninitialised byte during call to nfq_unbind_pf

fix valgrind errors of uninitialised byte during call to nfq_unbind_pf

Valgrind generates error reports during a call
to the nfq_unbind_pf function:

==00:00:00:08.662 22111== 4 errors in context 1 of 1:
==00:00:00:08.662 22111== Syscall param socketcall.sendto(msg) points
to uninitialised byte(s)
...
==00:00:00:08.662 22111== Uninitialised value was created by a stack allocation
==00:00:00:08.662 22111== at 0x679C30B: __build_send_cfg_msg
(libnetfilter_queue.c:178

Signed-off-by: Tamas K Lengyel <tamas.k.lengyel@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>