JDK-8137004: Memory leak caused by Parent#removed not being freed

[Chien Yang]

Hi Vadim,

Can you please review the proposed fix?

JIRA: https://bugs.openjdk.java.net/browse/JDK-8137004
Webrev: http://cr.openjdk.java.net/~ckyang/JDK-8137004/webrev.00/

Thanks,
- Chien