ssb: Try harder to avoid doing things with new connections during shutdown.

src/http.c

@@ -629,6 +629,12 @@ static void _http_on_connection(uv_stream_t* stream, int status)
 {
 	tf_http_listener_t* listener = stream->data;
 	tf_http_t* http = listener->http;
+	if (http->is_shutting_down)
+	{
+		tf_printf("Ignoring HTTP connection during shutdown.\n");
+		return;
+	}
+
 	tf_http_connection_t* connection = tf_malloc(sizeof(tf_http_connection_t));
 	*connection = (tf_http_connection_t) { .http = http, .tcp = { .data = connection }, .is_receiving_headers = true };
 	if (listener->tls)