jmx-dev RFR 8038794: java/lang/management/ThreadMXBean/SynchronizationStatistics.java fails intermittently

[Jaroslav Bachorik]

Please, review this test fix.

Issue : https://bugs.openjdk.java.net/browse/JDK-8038794
Webrev: http://cr.openjdk.java.net/~jbachorik/8038794/webrev.00

The problem described in this issue is that while a thread was blocked 
the blocked count reported by the MBean does not reflect it in very rare 
cases. However, it should be enough to wait a few moments to let the VM 
counter propagate the value to the MBean.

The attempted fix will cause the test to wait for the expected values 
instead of doing a one-time check. In the worst case the test will be 
timed out by the harness.

The rest of the changes just add more info to debug outputs.

Thanks,

-JB-