config: lower minRangeMaxBytes to 64 KB
config: lower minRangeMaxBytes to 64 KB

The lower minimum is useful for constructing clusters with lots of
ranges to test rebalancing heuristics.

paperstreet/cockroach,veteranlu/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,maxlang/cockroach,veteranlu/cockroach,glycerine/cockroach,petermattis/cockroach,maxlang/cockroach,petermattis/cockroach,veteranlu/cockroach,veteranlu/cockroach,paperstreet/cockroach,veteranlu/cockroach,petermattis/cockroach,petermattis/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,glycerine/cockroach,paperstreet/cockroach,maxlang/cockroach,veteranlu/cockroach,vaibhavarora/cockroach,petermattis/cockroach,petermattis/cockroach,vaibhavarora/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,petermattis/cockroach,maxlang/cockroach,paperstreet/cockroach,paperstreet/cockroach,glycerine/cockroach,vaibhavarora/cockroach,maxlang/cockroach,glycerine/cockroach,veteranlu/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,glycerine/cockroach,petermattis/cockroach,glycerine/cockroach,glycerine/cockroach,maxlang/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,maxlang/cockroach