ipvs: provide iph to schedulers

Before now the schedulers needed access only to IP
addresses and it was easy to get them from skb by
using ip_vs_fill_iph_addr_only.

New changes for the SH scheduler will need the protocol
and ports which is difficult to get from skb for the
IPv6 case. As we have all the data in the iph structure,
to avoid the same slow lookups provide the iph to schedulers.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Acked-by: Hans Schillstrom <hans@schillstrom.com>
Signed-off-by: Simon Horman <horms@verge.net.au>