IPVS: netns to services part 1

Services hash tables got netns ptr a hash arg,
While Real Servers (rs) has been moved to ipvs struct.
Two new inline functions added to get net ptr from skb.

Since ip_vs is called from different contexts there is two
places to dig for the net ptr skb->dev or skb->sk
this is handled in skb_net() and skb_sknet()

Global functions, ip_vs_service_get() ip_vs_lookup_real_service()
etc have got  struct net *net as first param.
If possible get net ptr skb etc,
 - if not &init_net is used at this early stage of patching.

ip_vs_ctl.c  procfs not ready for netns yet.

*v3
 Comments by Julian
- __ip_vs_service_find and __ip_vs_svc_fwm_find are fast path,
  net_eq(svc->net, net) so the check is at the end now.
- net = skb_net(skb) in ip_vs_out moved after check for skb_dst.

Signed-off-by: Hans Schillstrom <hans.schillstrom@ericsson.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>