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: Hans Schillstrom <[e-mail]>
Signed-off-by: Simon Horman <[e-mail]>

include/net/ip_vs.h

···
 	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 */