net/sched: act_ct: Fix flow table lookup after ct clear or switching zones

commit 2f131de3 upstream.

Flow table lookup is skipped if packet either went through ct clear
action (which set the IP_CT_UNTRACKED flag on the packet), or while
switching zones and there is already a connection associated with
the packet. This will result in no SW offload of the connection,
and the and connection not being removed from flow table with
TCP teardown (fin/rst packet).

To fix the above, remove these unneccary checks in flow
table lookup.

Fixes: 46475bb2

 ("net/sched: act_ct: Software offload of established flows")
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>