iptables-test: Use iptables implementation from core

iptables-test: Use iptables implementation from core

With the recent changes to iptables.c and the new API iptables-test.c
and iptables.c started to diverge and it is not really possible to
keep those two files in sync. Instead we start using the new API.

Unfortunatly, we need to partially parse argv and concatinate the rest
again together. This is ugly but not much we can do about it.