RFR: 8208278: [mlvm] Deadlocked threads are not always detected

[David Holmes]

webrev: http://cr.openjdk.java.net/~dholmes/8208278/webrev/
bug: https://bugs.openjdk.java.net/browse/JDK-8208278

The test was failing to find the expected deadlocks on OS X but it turns 
out that the test was simply racy and the race always lost on OS X. With 
logging enabled the test started failing on different platforms and in 
different ways.

The main logic of the test is restructured so that we don't assume 
things will happen within a certain time but instead we loop (or block) 
until they do and rely on the overall test timeout to detect there may 
be a problem.

Thanks,
David