net/mlx5: CT: Fix incorrect removal of tuple_nat_node from nat rhashtable

If a non nat tuple entry is inserted just to the regular tuples
rhashtable (ct_tuples_ht) and not to natted tuples rhashtable
(ct_nat_tuples_ht). Commit bc562be9 ("net/mlx5e: CT: Save ct entries
tuples in hashtables") mixed up the return labels and names sot that on
cleanup or failure we still try to remove for the natted tuples rhashtable.

Fix that by correctly checking if a natted tuples insertion
before removing it. While here make it more readable.

Fixes: bc562be9

 ("net/mlx5e: CT: Save ct entries tuples in hashtables")
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>