update iptables rules for more useful debugging

As discussed with dansmith in #openstack-nova,
iptables --line-numbers -L -nv is a more useful representation of
the iptables dump for determining network issues.

Related-Bug: #1298472

Change-Id: Ibae97f7a0cf29105e3601eca8ce24b8271a3a13d
Merge "update iptables rules for more useful debugging"