BUG/MINOR: http-ana: Increment scf bytes_out value if an haproxy error is sent

When an HAproxy error is sent, we must not forget to increment bytes_out
value on the front stconn.

This patch must be backport to 3.3.

src/http_ana.c

@@ -4765,6 +4765,7 @@ int http_forward_proxy_resp(struct stream *s, int final)
 	data = htx->data - co_data(res);
 	c_adv(res, data);
 	htx->first = -1;
+	s->scf->bytes_out += data;
 	return 1;
 }