Fix tests that don't catch asynchronous errors from isolate spawning. Update co19 status.

tests/isolate/issue_21398_parent_isolate2_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Note: the following comment is used by test.dart to additionally compile the
 // other isolate's code.
 // OtherScripts=deferred_loaded_lib.dart
 
 import 'dart:isolate';
 import 'dart:async';
 import "package:expect/expect.dart";
+import 'package:async_helper/async_helper.dart';
 
 import "deferred_loaded_lib.dart" deferred as lib;
 
 // In this test case we send an object created from a deferred library
 // that is loaded in the child isolate but not the parent isolate. The
 // parent isolate does not know about the type of this object and throws
 // an unhandled exception.
 funcChild(args) {
   var replyPort = args[0];
   // Deferred load a library, create an object from that library and send
   // it over to the parent isolate which has not yet loaded that library.
   lib.loadLibrary().then((_) {
     replyPort.send(new lib.FromChildIsolate());
   });
 }
 
 void helperFunction() {
   var receivePort = new ReceivePort();
+  asyncStart();
 
   // Spawn an isolate using spawnFunction.
   Isolate.spawn(funcChild, [receivePort.sendPort]).then(
     (isolate) {
       receivePort.listen(
         (msg) {
           // We don't expect to receive any valid messages.
           Expect.fail("We don't expect to receive any valid messages");
           receivePort.close();
+          asyncEnd();
         },
         onError: (e) {
           // We don't expect to receive any error messages, per spec listen
           // does not receive an error object.
           Expect.fail("We don't expect to receive any error messages");
           receivePort.close();
+          asyncEnd();
         }
       );
     }
   );
 }
 
 main() {
   helperFunction(); /// 01: runtime error
 }