RFR: 8269478: Shenandoah: gc/shenandoah/mxbeans tests should fail when no notifications arrive

[Roman Kennke]

On Mon, 28 Jun 2021 10:07:30 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> After JDK-8259954, some mxbeans tests wait in the effectively infinite loop for the notifications to arrive. If notifications are broken, it would wait forever, and test would timeout. We need to make such failure mode more straightforward.
> 
> Additional testing: 
>  - [x] Linux x86_64 fastdebug `gc/shenandoah/mxbeans` 
>  - [x] Linux x86_64 fastdebug `gc/shenandoah/mxbeans`, `-Xcomp`

Looks good. Thanks!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4611