RFR 8077327: ThreadStackTrace.java throws exception: BlockedThread expected to have BLOCKED but got RUNNABLE

[Jaroslav Bachorik]

Please, review the following test change

Issue : https://bugs.openjdk.java.net/browse/JDK-8077327
Webrev: http://cr.openjdk.java.net/~jbachorik/8077327/webrev.00

This fix is for an intermittent failure due to timing issues. The test 
is using an arbitrary waiting period to allow the tested thread to 
arrive to the requested state. Usually it works fine but under eg. heavy 
load this strategy will fail. The proposed solution is to explicitly 
check for the test thread arriving to the requested state instead of 
waiting eg. 10ms.

I also took the liberty of removing the custom Semaphore implementation 
and replacing its usage with java.util.concurrent.Phaser

Thanks,

-JB-