Process outstanding events before making a new HTTP client request

tests/standalone/io/https_bad_certificate_test.dart

Index: tests/standalone/io/https_bad_certificate_test.dart
diff --git a/tests/standalone/io/https_bad_certificate_test.dart b/tests/standalone/io/https_bad_certificate_test.dart
index e4f7dfb7078ecebf8836d0e3c55483d83f2adfa0..d07961a80a0912e70331f3666d5eed9c02a26d68 100644
--- a/tests/standalone/io/https_bad_certificate_test.dart
+++ b/tests/standalone/io/https_bad_certificate_test.dart
@@ -27,7 +27,7 @@ Future<SecureServerSocket> runServer() {
   });
 }
 
-void main() {
+main() async {
   var clientScript = Platform.script
                              .resolve('https_bad_certificate_client.dart')
                              .toFilePath();
@@ -46,12 +46,10 @@ void main() {
     });
   }
 
-  runServer().then((server) {
-    Future.wait([clientProcess(server.port, 'true'),
-                 clientProcess(server.port, 'false'),
-                 clientProcess(server.port, 'fisk'),
-                 clientProcess(server.port, 'exception')]).then((_) {
-      server.close();
-    });
-  });
+  var server = await runServer();
+  await clientProcess(server.port, 'true');
+  await clientProcess(server.port, 'false');
+  await clientProcess(server.port, 'fisk');
+  await clientProcess(server.port, 'exception');
+  server.close();
 }