fix/BROOKLYN-36

fix saveIptablesRules
Thanks @ahgittin for your comments.

My idea is slightly different: I wanted to make the `saveIptablesRules` more portable across distros.
For rhel/centos the suggested way is to use `service iptables save` while for debian/ubuntu it is available a package called `iptables-persistent` which install a service on the box that save the iptables rules any time they change, afaik.

Instead `iptables-save` seems misused here as it is generally useful when you want to export iptables rules to a file using i.e.: `iptables-save > /etc/sysconfig/iptables` and then `iptables-restore < /etc/sysconfig/iptables` but this doesn't look helpful here. wdyt?