CR 6860309 - solaris timing issue on thread startup

[Gary Adams]

  I've updated the webrev for CR#6860309 using a CountDownLatch.
The main thread will wait til both worker threads are ready to
block on the read() before the process is destroyed.

    http://cr.openjdk.java.net/~gadams/6860309/

Tested with -Xcomp, but still may need a older slow solaris/sparc
machine to confirm the fix works for the original bug
submitter.