Update unittest to new package layout.

utils/tests/pub/pub_install_hosted_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 a pub server', () {
     servePackages([package("foo", "1.2.3")]);
 
     appDir([dependency("foo", "1.2.3")]).scheduleCreate();
 
     schedulePub(args: ['install'],
         output: const RegExp("Dependencies installed!\$"));
 
@@ skipping 337 matching lines @@
 
     packagesDir({
       "foo": "1.0.0",
       "bar": null,
       "shared-dep": "1.0.0"
     }).scheduleValidate();
 
     run();
   });
 }