dumpstate: collect xtables based iface stats, update iptables info.

The newer kernels now have /proc/net/xt_qtaguid/iface_stat_fmt.
Add the extra iptables output and remove ip6tables for nat which doesn't
exist.

Change-Id: I819c707b337a707ca0acd87d9ab38cd68ca0f36c
1 file changed