RFR: Initial committed regions count can be more than max

[Roman Kennke]

Ok. (and wtf?)

Thanks,
Roman

> http://cr.openjdk.java.net/~shade/shenandoah/committed-max/webrev.01/
> 
> This hot-fixes the apparent off-by-one error in initial region count calculation. We normally deal
> with rounding errors by dealing with capacities in "region" units. That works well, but we also need
> to make sure the initial number of regions does not get more than max number of regions.
> 
> Separately, I shall look into the underlying issues why we have less "max" regions than "initial".
> The hotfix makes the downstream code correct meanwhile, and it makes sure failures are not cryptic,
> but actually asserted before pushing bad values down.
> 
> Testing: tier3_gc_shenandoah, failing ad-hoc tests
> 
> Thanks,
> -Aleksey
>