storage: extract TestReplicateAddAndRemove into two tests
storage: extract TestReplicateAddAndRemove into two tests

Also DRY while I'm here.

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