RFR: 8222667: vmTestbase/nsk/jdi/ThreadStartRequest/addThreadFilter/addthreadfilter002/TestDescription.java failed with "event IS NOT a breakpoint"

[Daniil Titov]

Please review the change that fixes the test that intermittently fails with Graal on.

The test tests  addThreadFilter() method for com.sun.jdi.ThreadStartRequest class. It starts a debuggee, creates ThreadStartRequest, enables it, and calls addThreadFilter(). The test also uses breakpoints to synchronize with the debuggee,  but the problem here is that while waiting for a breakpoint event, occasionally, when Graal is on, the event the test receives is a ThreadStartEvent for " HotSpotGraalManagement Bean Registration" thread, rather than a breakpoint event. The test doesn't expect it and fails. 

The fix takes this into account and makes the test keep waiting for a breakpoint event instead of failing.

Webrev: http://cr.openjdk.java.net/~dtitov/8222667/webrev.01/
Bug: https://bugs.openjdk.java.net/browse/JDK-8222667

Thanks!
--Daniil