netfilter: ipv6: move xfrm_lookup at end of ip6_route_me_harder

xfrm_lookup should be called after ip6_route_output skb_dst_set,
otherwise skb_dst_set of xfrm_lookup is pointless

Signed-off-by: Ulrich Weber <uweber@astaro.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>