ipvs: use list_del_init instead of list_del/INIT_LIST_HEAD

Using list_del_init() instead of list_del() + INIT_LIST_HEAD().

spatch with a semantic match is used to found this problem.
(http://coccinelle.lip6.fr/

)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>