ipvs: add ip_vs_status info

ipvs: add ip_vs_status info

Add /proc/net/ip_vs_status to show current state of IPVS.

The motivation for this new /proc interface is to provide the output
for the users to help them decide when to tune the load factor for
hash tables, which is possible with the new sysctl knobs coming in
followup patch.

The output also includes information for the kthreads used for stats.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Florian Westphal <fw@strlen.de>