add iptables to installed packages

[Ben]

iptables is used by fail2ban and isn't installed in the container packages. this causes fail2ban to fail and log errors.

adding it to https://github.com/iredmail/dockerized/blob/master/scripts/install_all_pkgs.sh should address the problems.

change line 26 from:

PKGS_FAIL2BAN="fail2ban bind9-dnsutils"

to

PKGS_FAIL2BAN="iptables fail2ban bind9-dnsutils"

[Ben]

Thanks for the quick update! Is there a new stable tag build coming soon?