RFR (M): 8233588: Clean up SurvRateGroup

[Kim Barrett]

> On Nov 19, 2019, at 10:01 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> So fixed in
> 
> http://cr.openjdk.java.net/~tschatzl/8233588/webrev.0_to_1/
> http://cr.openjdk.java.net/~tschatzl/8233588/webrev.1/
> 
> Passed jtreg gc/g1 testing
> 
> Thanks,
>  Thomas

Looks good.