Fix analysis server asynchrony test.

pkg/analysis_server/test/integration/asynchrony_test.dart

 // Copyright (c) 2014, 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.
 
 library test.integration.analysis.error;
 
 import 'dart:async';
 
 import 'package:unittest/unittest.dart';
 
@@ skipping 33 matching lines @@
       lastMessageResult = server.send('server.getVersion', null);
     }
 
     // Flush the server's standard input stream to verify that it has really
     // received them all.  If the server is blocked waiting for us to read
     // its responses, the flush will never complete.
     return server.flushCommands().then((_) {
 
       // Begin processing responses from the server.
       server.listenToOutput((String event, params) {
-        // No notifications are expected.
-        fail('Unexpected notification: $event');
+        // The only expected notification is server.connected.
+        if (event != 'server.connected') {
+          fail('Unexpected notification: $event');
+        }
       });
 
       // Terminate the test when the response to the last message is received.
-      lastMessageResult.then((_) {
+      return lastMessageResult.then((_) {
         server.send("server.shutdown", null).then((_) {
           return server.exitCode;
         });
       });
     });
   }
 }
 
 main() {
   runReflectiveTests(AsynchronyIntegrationTest);
 }