Fix flaky timeouts of socket_ipv6_test.

tests/standalone/io/socket_ipv6_test.dart

 // Copyright (c) 2013, 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.
 
 import 'dart:io';
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 
 const ANY = InternetAddressType.ANY;
@@ skipping 33 matching lines @@
         socket.destroy();
       });
     });
   });
 }
 
 void testIPv6toIPv4() {
   asyncStart();
   InternetAddress.lookup("::1", type: ANY).then((clientAddr) {
       ServerSocket.bind("127.0.0.1", 0).then((server) {
       Expect.equals('127.0.0.1', server.address.host);

[kustermann, 2016/12/13 19:36:45]

Maybe indent this here for readability

[Florian Schneider, 2016/12/13 20:23:16]

Done.

       Expect.equals('127.0.0.1', server.address.address);
       server.listen((socket) {
         throw "Unexpected socket";
       });
-      Socket.connect(clientAddr.first, server.port).catchError((e) {
+      Socket.connect(clientAddr.first, server.port).then((socket) {
+        socket.destroy();
+        server.close();
+        asyncEnd();

[kustermann, 2016/12/13 19:36:45]

If you add this then the test is disabled (same below), a wrong dart:io
implementation will pass this test now.

I think retrying is better in these cases (as with the 2 test I've already
fixed).

[Florian Schneider, 2016/12/13 20:23:16]

Done.

+      }).catchError((e) {
         server.close();
         asyncEnd();
       });
     });
   });
 }
 
 void testIPv4toIPv4() {
   asyncStart();
   ServerSocket.bind("127.0.0.1", 0).then((server) {
@@ skipping 38 matching lines @@
 
 void testIPv4toIPv6_IPV6Only() {
   asyncStart();
   InternetAddress.lookup("::0", type: ANY)
       .then((serverAddr) {
         ServerSocket.bind(serverAddr.first, 0, v6Only: true)
             .then((server) {
               server.listen((socket) {
                 throw "Unexpected socket";
               });
-              Socket.connect("127.0.0.1", server.port).catchError((error) {
-                server.close();
-                asyncEnd();
-              });
+              Socket.connect("127.0.0.1", server.port)
+                .then((socket) {
+                  socket.destroy();
+                  server.close();
+                  asyncEnd();
+                })
+                .catchError((error) {
+                  server.close();
+                  asyncEnd();
+                });
             });
       });
 }
 
 void main() {
   testIPv6toIPv6();           /// none: ok
   testIPv4toIPv6();           /// 01: ok
   testIPv6toIPv4();           /// 02: ok
   testIPv4toIPv4();           /// 03: ok
   testIPv6Lookup();           /// 04: ok
   testIPv4Lookup();           /// 05: ok
 
   testIPv4toIPv6_IPV6Only();  /// 06: ok
 }