RFR: JDK-8284874: Add comment to ProcessHandle/OnExitTest to describe zombie problem [v3]

[Roger Riggs]

On Thu, 14 Apr 2022 18:29:21 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> ProcessHandle/OnExitTest is vulnerable to misconfigured systems that do not reap zombies in a timely fashion. [JDK-8284282](https://bugs.openjdk.java.net/browse/JDK-8284282) describes this problem in detail.
>> 
>> Until we figure out a way to fix that (if at all - see comments in JBS), let us have a clarifying comment in the test itself.
>
> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix copyright

Marked as reviewed by rriggs (Reviewer).

Core-libs issues only require 1 reviewer; though some more complex issues deserve more than 1.
Thanks

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PR: https://git.openjdk.java.net/jdk/pull/8240