openvswitch: Fix template leak in error cases.

Commit 5b48bb8506c5 ("openvswitch: Fix helper reference leak") fixed a
reference leak on helper objects, but inadvertently introduced a leak on
the ct template.

Previously, ct_info.ct->general.use was initialized to 0 by
nf_ct_tmpl_alloc() and only incremented when ovs_ct_copy_action()
returned successful. If an error occurred while adding the helper or
adding the action to the actions buffer, the __ovs_ct_free_action()
cleanup would use nf_ct_put() to free the entry; However, this relies on
atomic_dec_and_test(ct_info.ct->general.use). This reference must be
incremented first, or nf_ct_put() will never free it.

Fix the issue by acquiring a reference to the template immediately after
allocation.

Fixes: cae3a262 ("openvswitch: Allow attaching helpers to ct action")
Fixes: 5b48bb8506c5 ("openvswitch: Fix helper reference leak")
Signed-off-by: Joe Stringer <joe@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>