Modify tests to use Directory.systemTemp

tests/standalone/io/http_client_connect_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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import 'dart:async';
@@ skipping 78 matching lines @@
       request.response.contentLength = 100;
       request.response.write("data");
       request.response.write("more data");
       completer.future.then((_) => server.close());
     });
 
     var client = new HttpClient();
     client.get("127.0.0.1", server.port, "/")
       .then((request) => request.close())
       .then((response) {
-        // Close the (incomplete) response, now we have seen the response object.
+        // Close the (incomplete) response, now that we have seen
+        // the response object.
         completer.complete(null);
         int errors = 0;
         response.listen(
           (data) {},
           onError: (error) => errors++,
           onDone: () {
             Expect.equals(1, errors);
             asyncEnd();
           });
       });
@@ skipping 17 matching lines @@
 
 
 void main() {
   testGetEmptyRequest();
   testGetDataRequest();
   testGetInvalidHost();
   testGetServerClose();
   testGetDataServerClose();
   testPostEmptyRequest();
 }