RFR for JDK-8023462: TEST_BUG: test/com/sun/net/httpserver/bugs/B6433018.java fails on slow/single core machine

[Tristan Yan]

Hi Everyone

Please review the fix for JDK-8023462 
<https://bugs.openjdk.java.net/browse/JDK-8023462>.

Description:
This test is using Thread.sleep(3000) to sync between server and client, 
this could be wrong when running is slow machine. I am trying to use 
modern CountDownLatch sync server and client.

http://cr.openjdk.java.net/~pzhang/Tristan/8023462/webrev/

Thank you
Tristan