net: Convert clusterip_net_ops

These pernet_operations register and unregister nf hooks,
and populate and destroy /proc entry. So, they are able
to be marked as async.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ipt_CLUSTERIP.c

@@ -840,6 +840,7 @@ static struct pernet_operations clusterip_net_ops = {
 	.exit = clusterip_net_exit,
 	.id   = &clusterip_net_id,
 	.size = sizeof(struct clusterip_net),
+	.async = true,
 };
 
 static int __init clusterip_tg_init(void)