Enable a couple of tests that were disabled because they

tests/standalone/io/http_headers_state_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.
 //
 
 import "dart:isolate";
 import "dart:io";
 
 void test(int totalConnections, [String body]) {
   HttpServer server = new HttpServer();
@@ skipping 53 matching lines @@
         server.close();
       }
     };
   }
 }
 
 void main() {
   test(5);
   test(5, "Hello and goodbye");
 }