Make "--no-packages-dir" the default.

test/get/hosted/gets_a_package_with_busted_dev_dependencies_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.
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   // Regression test for issue 22194.
   integration('gets a dependency with broken dev dependencies from a pub '
       'server', () {
     servePackages((builder) {
       builder.serve("foo", "1.2.3", pubspec: {
         "dev_dependencies": {
           "busted": {"not a real source": null}
         }
       });
     });
 
     d.appDir({"foo": "1.2.3"}).create();
 
     pubGet();
 
     d.cacheDir({"foo": "1.2.3"}).validate();
-    d.packagesDir({"foo": "1.2.3"}).validate();
+    d.appPackagesFile({"foo": "1.2.3"}).validate();
   });
 }