Fix a bunch of pub tests that started running "pub get".

test/dart2js/passes_along_environment_constants_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
@@ skipping 10 matching lines @@
         d.file("main.dart", """
 void main() {
   if (const bool.fromEnvironment('CONSTANT')) {
     print("hello");
   }
 }
 """)
       ])
     ]).create();
 
-    pubServe();
+    pubServe(shouldGetFirst: true);
     requestShouldSucceed("main.dart.js", contains("hello"));
     endPubServe();
   });
 }