RFR 9: 8085980 java/lang/ProcessHandle/TreeTest.java: AssertionError: Wrong number of spawned children

[Roger Riggs]

Please review changes to the ProcessHandle TreeTest to address intermittent failures. 
Since spurious processes have been observed, the test only tracks the subprocesses 
it launches and ignores unknown subprocesses.The end-of-test cleanup is more rigorous. 

Webrev: 
http://cr.openjdk.java.net/~rriggs/webrev-tree-8085980/ 

Issue: 
https://bugs.openjdk.java.net/browse/JDK-8085980 

Thanks, Roger