route: Take the right src and dst addresses in ip_route_newports

When we set up the flow informations in ip_route_newports(), we take
the address informations from the the rt_key_src and rt_key_dst fields
of the rtable. They appear to be empty. So take the address
informations from rt_src and rt_dst instead. This issue was introduced
by commit 5e2b61f7 ("ipv4: Remove
flowi from struct rtable.")

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>