ipvs: Don't use current in proc_do_defense_mode

Instead store ipvs in extra2 so that proc_do_defense_mode can easily
find the ipvs that it's value is associated with.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>