storage: deflake TestBaseQueuePurgatory
storage: deflake TestBaseQueuePurgatory

Fixes #6342.

glycerine/cockroach,petermattis/cockroach,cockroachdb/cockroach,veteranlu/cockroach,paperstreet/cockroach,cockroachdb/cockroach,glycerine/cockroach,petermattis/cockroach,sunya123/cockroach,petermattis/cockroach,sunya123/cockroach,cockroachdb/cockroach,maxlang/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,sunya123/cockroach,maxlang/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,paperstreet/cockroach,maxlang/cockroach,petermattis/cockroach,cockroachdb/cockroach,petermattis/cockroach,arjun4084346/cockroach,petermattis/cockroach,arjun4084346/cockroach,maxlang/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,maxlang/cockroach,maxlang/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,maxlang/cockroach,glycerine/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,sunya123/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,maxlang/cockroach,vaibhavarora/cockroach,sunya123/cockroach,paperstreet/cockroach,cockroachdb/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,glycerine/cockroach,arjun4084346/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,glycerine/cockroach,petermattis/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,sunya123/cockroach,paperstreet/cockroach,vivekmenezes/cockroach,sunya123/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,glycerine/cockroach,glycerine/cockroach,veteranlu/cockroach,petermattis/cockroach,vaibhavarora/cockroach,vivekmenezes/cockroach,sunya123/cockroach,glycerine/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,arjun4084346/cockroach