Use half-close when closing the socking in HttpServerEarlyClientCloseTest.

tests/standalone/src/io/HttpServerEarlyClientCloseTest.dart

 #import("dart:io");
 #import("dart:isolate");
 
 void sendData(List<int> data, int port) {
   Socket socket = new Socket("127.0.0.1", port);
   socket.onConnect = () {
     socket.onData = () {
       Expect.fail("No data response was expected");
     };
     socket.outputStream.onNoPendingWrites = () {
-      socket.close(false);
+      socket.close(true);
     };
     socket.outputStream.write(data);
   };
 }
 
 class EarlyCloseTest {
   EarlyCloseTest(Object this.data,
                  String this.exception,
                  [bool this.expectRequest = false]);
 
@@ skipping 63 matching lines @@
     } else {
       server.close();
     }
   }
   runTest(tests.iterator());
 }
 
 void main() {
   testEarlyClose();
 }