[IPV4]: Always set fl.proto in ip_route_newports

ip_route_newports uses the struct flowi from the struct rtable returned
by ip_route_connect for the new route lookup and just replaces the port
numbers if they have changed. If an IPsec policy exists which doesn't match
port 0 the struct flowi won't have the proto field set and no xfrm lookup
is done for the changed ports.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>