iptables-unit: Check if rules are inserted/removed

iptables-unit: Check if rules are inserted/removed

Optionally use iptables-save to check if the rules are installed or
removed on the system instead of relying only on the returned iptables
error code.

Do notice that running tools/iptables-unit will modify and delete existing
iptables firewall rules on your system. Use iptables-unit with caution!