RFR 8024660: TEST_BUG: java/lang/ProcessBuilder/*IOHandle.java leaving hotspot.log open in fastdebug builds

[Pavel Punegov]

Please review this fix for the test bug

Issue: https://bugs.openjdk.java.net/browse/JDK-8024660
Webrev: http://cr.openjdk.java.net/~robm/8024660/webrev.01/

Summary:
 Add a wait for process C finish before we return and pass the test.

There are also some code improvements made for easier code reading.

Thanks,
Pavel