Fix analyzer hints and warnings in test/.

test/snapshot/doesnt_snapshot_transitive_dependencies_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.
 
 library pub_tests;
 
 import 'package:path/path.dart' as p;
-import 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 
 main() {
   integration("doesn't create a snapshot for transitive dependencies' "
       "executables", () {
     servePackages((builder) {
       builder.serve("foo", "1.2.3", deps: {'bar': '1.2.3'});
       builder.serve("bar", "1.2.3", contents: [
         d.dir("bin", [d.file("hello.dart", "void main() => print('hello!');")])
       ]);
     });
 
     d.appDir({"foo": "1.2.3"}).create();
 
     pubGet();
 
     d.nothing(p.join(appPath, '.pub', 'bin', 'bar')).validate();
   });
 }