sctp: make sctp over IPv6 work with IPsec

SCTP never called xfrm_output after it's v6 route lookups so
that never really worked with ipsec.  Additioanlly, we never
passed port nubmers and protocol in the flowi, so any port
based policies were never applied as well.  Now that we can
fixed ipv6 routing lookup code, using ip6_dst_lookup_flow()
and pass port numbers.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>