RFR 8200706: Better cleanup for open/test/jdk/java/lang/ProcessBuilder/DestroyTest.java

[Roger Riggs]

Please review an intermittent test bug/cleanup improvement that places 
temporary
files in the directory that is auto-cleaned by jtreg.

Webrev:
  http://cr.openjdk.java.net/~rriggs/webrev-clean-destroy-8200706/

Thanks, Roger