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

test/get/git/stay_locked_if_compatible_test.dart

 // Copyright (c) 2012, 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() {
   integration("doesn't upgrade a locked Git package with a new compatible "
       "constraint", () {
     ensureGit();
 
     d.git('foo.git', [
       d.libDir('foo', 'foo 1.0.0'),
       d.libPubspec("foo", "1.0.0")
     ]).create();
 
     d.appDir({"foo": {"git": "../foo.git"}}).create();
 
-    pubGet();
+    pubGet(args: ["--packages-dir"]);
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo 1.0.0";')
       ])
     ]).validate();
 
     d.git('foo.git', [
       d.libDir('foo', 'foo 1.0.1'),
       d.libPubspec("foo", "1.0.1")
     ]).commit();
 
     d.appDir({"foo": {"git": "../foo.git", "version": ">=1.0.0"}}).create();
 
-    pubGet();
+    pubGet(args: ["--packages-dir"]);
 
     d.dir(packagesPath, [
       d.dir('foo', [
         d.file('foo.dart', 'main() => "foo 1.0.0";')
       ])
     ]).validate();
   });
 }