RFR (S) 8225111: Make Shenandoah tests work with 32-bit VMs

[Roman Kennke]

Ok. Thanks!
Roman


> RFE:
>   https://bugs.openjdk.java.net/browse/JDK-8225111
> 
> On the second thought, I want to split these test changes from the x86_32 support patch. This allows
> other 32-bit targets to work as well, and it would only require to backport this smaller test bunch,
> without dragging x86_32 in.
> 
> This only touches Shenandoah tests:
>   http://cr.openjdk.java.net/~shade/8225111/webrev.01/
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>