Ipv6 support for iptables

Signed-off-by: Justin Santa Barbara <justin@fathomdb.com>
Make sure IPv6 is enabled on the bridge, for IPv6

Signed-off-by: Justin Santa Barbara <justin@fathomdb.com>
Skip the first IP for IPv6 as well

Otherwise this forces use of a configured subnet.

Signed-off-by: Justin Santa Barbara <justin@fathomdb.com>