netfilter: nf_tables: fix flush after rule deletion in the same batch

Flush after rule deletion bogusly hits -ENOENT. Skip rules that have
been already from nft_delrule_by_chain() which is always called from the
flush path.

Fixes: cf9dc09d ("netfilter: nf_tables: fix missing rules flushing per table")
Reported-by: Phil Sutter <phil@nwl.cc>
Acked-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -313,6 +313,9 @@ static int nft_delrule_by_chain(struct nft_ctx *ctx)
 	int err;
 
 	list_for_each_entry(rule, &ctx->chain->rules, list) {
+		if (!nft_is_active_next(ctx->net, rule))
+			continue;
+
 		err = nft_delrule(ctx, rule);
 		if (err < 0)
 			return err;