Update unittest to new package layout.

utils/tests/archive/utils_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('utils_test');
 
-#import('../../../pkg/unittest/unittest.dart');
+#import('../../../pkg/unittest/lib/unittest.dart');
 #import('../../archive/utils.dart');
 
 main() {
   // TODO(nweiz): re-enable this once issue 4378 is fixed.
   return;
 
   group('attachFinalizer', () {
     test('calls the finalizer eventually once the object is collected', () {
       var finalized = null;
 
@@ skipping 15 matching lines @@
       void finalizer(String data) {
         finalized = data;
       }
 
       var list = [1, 2, 3];
       attachFinalizer(list, finalizer, 'finally finalized!');
       expect(finalized, isNull);
     });
   });
 }