RFR 9: [TESTBUG] 8160151: java/lang/ProcessBuilder/Zombies.java failed with error "1 zombies!"

[Roger Riggs]

Please review a test fix for an intermittently failing ProcessBuilder test.
The test should be run in a separate vm so it only sees Zombies from 
processes it creates.
When run in-process with jtreg, it may see Zombies from other processes 
created by jtreg.
Additional diagnostic information is added as well in case of recurrence.

The test is moved back to tier1.

Webrev:
   http://cr.openjdk.java.net/~rriggs/webrev-zombies-8160151/

Issue:
   https://bugs.openjdk.java.net/browse/JDK-8160151

Thanks, Roger