JDK 9 RFR of JDK-8143097: Test java/net/ipv6tests/UdpTest.java fails

[Amy Lu]

Please reviewthe patch for java/net/ipv6tests/UdpTest.java

bug: https://bugs.openjdk.java.net/browse/JDK-8143097
webrev: http://cr.openjdk.java.net/~amlu/8143097/webrev.00/

This test fails intermittently in a test scenario for checking 
DatagramSocket (with SO_TIMEOUT enabled) 'receive'works even after a 
delay (but within the specified timeout):

  120     static void test2 () throws Exception {
  121         s1 = new DatagramSocket ();
  ......
  151         s1.setSoTimeout(10000);
  152         runAfter (2000, new Runnable () { <<<< --- run after the 
given time (2000) has elapsed
  153             public void run () {
  ......
  156                     s.send (p);
  ......
  158             }
  159         });
  160         t1 = System.currentTimeMillis();
  161         s1.receive (new DatagramPacket (new byte [128], 128)); 
<<<< ---receive should works here
  162         checkTime (System.currentTimeMillis() - t1, 4000);

The final checkTime method is for checking the time got 
(System.currentTimeMillis() - t1) is equal to (with 50% tolerance) the 
time expected (4000). This assumption is not correct. Test should check 
that the time got (System.currentTimeMillis() - t1) is between 2000 (the 
given delay) and 10000 (the given timeout).

Thanks,
Amy