Update unittest to new package layout.

utils/tests/pub/pub_install_sdk_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.
 
 #library('pub_tests');
 
 #import('dart:io');
 
 #import('test_pub.dart');
-#import('../../../pkg/unittest/unittest.dart');
+#import('../../../pkg/unittest/lib/unittest.dart');
 
 main() {
   test('checks out a package from the SDK', () {
     dir(sdkPath, [
       file('revision', '1234'),
       dir('pkg', [
         dir('foo', [
           libDir('foo', 'foo 0.0.1234')
         ])
       ])
     ]).scheduleCreate();
 
     dir(appPath, [
       pubspec({"name": "myapp", "dependencies": {"foo": {"sdk": "foo"}}})
     ]).scheduleCreate();
 
     schedulePub(args: ['install'],
         output: '''
         Dependencies installed!
         ''');
 
     packagesDir({"foo": "0.0.1234"}).scheduleValidate();
 
     run();
   });
 }