IPVS: netns, ip_vs_stats and its procfs

The statistic counter locks for every packet are now removed,
and that statistic is now per CPU, i.e. no locks needed.
However summing is made in ip_vs_est into ip_vs_stats struct
which is moved to ipvs struc.

procfs, ip_vs_stats now have a "per cpu" count and a grand total.
A new function seq_file_single_net() in ip_vs.h created for handling of
single_open_net() since it does not place net ptr in a struct, like others.

/var/lib/lxc # cat /proc/net/ip_vs_stats_percpu
       Total Incoming Outgoing         Incoming         Outgoing
CPU    Conns  Packets  Packets            Bytes            Bytes
  0        0        3        1               9D               34
  1        0        1        2               49               70
  2        0        1        2               34               76
  3        1        2        2               70               74
  ~        1        7        7              18A              18E

     Conns/s   Pkts/s   Pkts/s          Bytes/s          Bytes/s
           0        0        0                0                0

*v3
ip_vs_stats reamains as before, instead ip_vs_stats_percpu is added.
u64 seq lock added

*v4
Bug correction inbytes and outbytes as own vars..
per_cpu counter for all stats now as suggested by Julian.

[horms@verge.net.au: removed whitespace-change-only hunk]
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>