RFR: Fix up pointer volatility

[Roman Kennke]

Yes


> Hi,
>
> Scanned through our changes against upstream to see if we get pointer volatility
> right everywhere. We seem to be, and the only missing place is this:
>
> diff -r 71ef78a756e7 src/share/vm/gc/shenandoah/shenandoahHeap.hpp
> --- a/src/share/vm/gc/shenandoah/shenandoahHeap.hpp	Fri May 12 12:51:33 2017 +0200
> +++ b/src/share/vm/gc/shenandoah/shenandoahHeap.hpp	Fri May 12 13:21:39 2017 +0200
> @@ -201,7 +201,7 @@
>    ShenandoahConnectionMatrix* _connection_matrix;
>
>  #ifdef ASSERT
> -  volatile Thread* _heap_lock_owner;
> +  Thread* volatile _heap_lock_owner;
>  #endif
>
>  public:
>
> Testing: hotspot_gc_shenandoah
>
> Thanks,
> -Aleksey
>