openvswitch: add seqadj extension when NAT is used.

openvswitch: add seqadj extension when NAT is used.

When the conntrack is initialized, there is no helper attached
yet so the nat info initialization (nf_nat_setup_info) skips
adding the seqadj ext.

A helper is attached later when the conntrack is not confirmed
but is going to be committed. In this case, if NAT is needed then
adds the seqadj ext as well.

Fixes: 16ec3d4fbb96 ("openvswitch: Fix cached ct with helper.")
Signed-off-by: Flavio Leitner <fbl@sysclose.org>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>