IPVS: fix netns if reading ip_vs_* procfs entries

Without this patch every access to ip_vs in procfs will increase
the netns count i.e. an unbalanced get_net()/put_net().
(ipvsadm commands also use procfs.)
The result is you can't exit a netns if reading ip_vs_* procfs entries.

Signed-off-by: Hans Schillstrom <hans.schillstrom@ericsson.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>