netfilter: nftables: skip hook overlap logic if flowtable is stale

If the flowtable has been previously removed in this batch, skip the
hook overlap checks. This fixes spurious EEXIST errors when removing and
adding the flowtable in the same batch.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -6783,6 +6783,9 @@ static int nft_register_flowtable_net_hooks(struct net *net,
 
 	list_for_each_entry(hook, hook_list, list) {
 		list_for_each_entry(ft, &table->flowtables, list) {
+			if (!nft_is_active_next(net, ft))
+				continue;
+
 			list_for_each_entry(hook2, &ft->hook_list, list) {
 				if (hook->ops.dev == hook2->ops.dev &&
 				    hook->ops.pf == hook2->ops.pf) {