Generate an error for active connections when the HTTP client is shutdown

tests/standalone/io/http_server_handler_test.dart

Index: tests/standalone/io/http_server_handler_test.dart
diff --git a/tests/standalone/io/http_server_handler_test.dart b/tests/standalone/io/http_server_handler_test.dart
index e44a6cf458eb0c38eef8eccece8fd075ebcee2d1..62d77ede50cd952d091dd9a9e06808c66a3e0ab4 100644
--- a/tests/standalone/io/http_server_handler_test.dart
+++ b/tests/standalone/io/http_server_handler_test.dart
@@ -101,7 +101,7 @@ void testDefaultHandler() {
       conn.onResponse = (HttpClientResponse response) {
         Expect.equals(HttpStatus.NOT_FOUND, response.statusCode);
         Expect.equals("Non Trouvé", response.reasonPhrase);
-        done();
+        response.inputStream.onClosed = done;
       };
       conn.onError = error;
     };