8003895: java/nio/channels/AsynchronousChannelGroup/Unbounded.java failing again [win64]

[Alan Bateman]

This test has failed a few times, always Windows.

The problem is the setup where the test creates 256 connections through 
the loopback. The tests doesn't set the listen backlog and periodically 
the connections aren't being accepted fast enough. To address this, I've 
changed the test so that the connections are accepted synchronously, 
that way the connections are established one-by-one before actual test 
happens. The webrev with the changes to the test is here:

http://cr.openjdk.java.net/~alanb/8003895/webrev/

-Alan.