ipvs: remove unused variable for ip_vs_new_dest

The dest variable is not used after ip_vs_new_dest anymore in
ip_vs_add_dest, do not need pass it to ip_vs_new_dest, remove it.

Signed-off-by: GuoYong Zheng <zhenggy@chinatelecom.cn>
Acked-by: Julian Anastasov <ja@ssi.bg>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>