Use the new test runner.

test/global/activate/different_version_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.
 
 import '../../test_pub.dart';
 
 main() {
-  initConfig();
   integration("discards the previous active version if it doesn't match the "
       "constraint", () {
     servePackages((builder) {
       builder.serve("foo", "1.0.0");
       builder.serve("foo", "2.0.0");
     });
 
     // Activate 1.0.0.
     schedulePub(args: ["global", "activate", "foo", "1.0.0"]);
 
     // Activating it again with a different constraint changes the version.
     schedulePub(args: ["global", "activate", "foo", ">1.0.0"], output: """
         Package foo is currently active at version 1.0.0.
         Resolving dependencies...
         + foo 2.0.0
         Downloading foo 2.0.0...
         Precompiling executables...
         Loading source assets...
         Activated foo 2.0.0.""");
   });
 }