[11] RFR: Drop the workaround for JDK-8217717

[Roman Kennke]

Yes, that looks good!

Roman


> Back when we backported self-fixing barriers, we had to include the workaround for JDK-8217717 [1]:
>   https://hg.openjdk.java.net/shenandoah/jdk11/rev/b16b63a399f3#l6.61
> 
> That workaround arrived through upstream 11.0.7 and no longer needed. Let's drop it:
>   https://cr.openjdk.java.net/~shade/shenandoah/11u-drop-8217717/webrev.01/
> 
> It seems to be exactly the same method that is in BarrierSetC1::resolve_address. I checked
> shenandoahBarrierSetC1.cpp is similar to what we have in jdk/jdk after this change.
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>