IPVS remove unused var from migration to netns

Remove variable ctl_key from struct netns_ipvs,
it's a leftover from early netns work.
Signed-off-by: NHans Schillstrom <hans.schillstrom@ericsson.com>
Signed-off-by: NSimon Horman <horms@verge.net.au>

include/net/ip_vs.h

@@ -836,8 +836,6 @@ struct netns_ipvs {
 	int			num_services;    /* no of virtual services */
 
 	rwlock_t		rs_lock;         /* real services table */
-	/* semaphore for IPVS sockopts. And, [gs]etsockopt may sleep. */
-	struct lock_class_key	ctl_key;	/* ctl_mutex debuging */
 	/* Trash for destinations */
 	struct list_head	dest_trash;
 	/* Service counters */