RFR: fix aarch64 membar elision with shenandoah

[Roman Kennke]

Am 16.07.2018 um 10:26 schrieb Roland Westrelin:
> 
>> Yes, but enqueue-barriers and satb-barriers are mutally exclusive. There
>> is no point in enabling both. In fact, we should check+verify that this
>> is not even attempted.
> 
> Can I push the change as it is then?


Have you posted a fix for the failing test? Or do you want us to take
care of it after you pushed?

Roman