fix up TestMultiRangeScanReverseScanInconsistent
fix up TestMultiRangeScanReverseScanInconsistent

it had a loop to work around non-changing timestamps,
but did not actually clean up the old versions, causing
test failures. in fact, cleanup is really hard there, so
we make sure to be more proactive about the choice of
timestamp instead.

cockroachdb/cockroach,bg451/cockroach,vivekmenezes/cockroach,il9ue/cockroach,maxlang/cockroach,cuongdo/cockroach,veteranlu/cockroach,arjun4084346/cockroach,veteranlu/cockroach,bg451/cockroach,cockroachdb/cockroach,sunya123/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,paperstreet/cockroach,sunya123/cockroach,maxlang/cockroach,bg451/cockroach,marcuswestin/cockroach,marcuswestin/cockroach,vaibhavarora/cockroach,glycerine/cockroach,arjun4084346/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,cuongdo/cockroach,maxlang/cockroach,glycerine/cockroach,nieyy/cockroach,petermattis/cockroach,maxlang/cockroach,il9ue/cockroach,il9ue/cockroach,marcuswestin/cockroach,veteranlu/cockroach,il9ue/cockroach,petermattis/cockroach,marcuswestin/cockroach,glycerine/cockroach,nieyy/cockroach,sunya123/cockroach,cuongdo/cockroach,nieyy/cockroach,vivekmenezes/cockroach,il9ue/cockroach,vivekmenezes/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,petermattis/cockroach,arjun4084346/cockroach,veteranlu/cockroach,marcuswestin/cockroach,petermattis/cockroach,veteranlu/cockroach,sunya123/cockroach,cuongdo/cockroach,petermattis/cockroach,cockroachdb/cockroach,arjun4084346/cockroach,vaibhavarora/cockroach,petermattis/cockroach,il9ue/cockroach,glycerine/cockroach,paperstreet/cockroach,nieyy/cockroach,sunya123/cockroach,marcuswestin/cockroach,cuongdo/cockroach,paperstreet/cockroach,nieyy/cockroach,nieyy/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,bg451/cockroach,sunya123/cockroach,glycerine/cockroach,petermattis/cockroach,vivekmenezes/cockroach,bg451/cockroach,cockroachdb/cockroach,glycerine/cockroach,glycerine/cockroach,paperstreet/cockroach,paperstreet/cockroach,bg451/cockroach,bg451/cockroach,vaibhavarora/cockroach,maxlang/cockroach,glycerine/cockroach,marcuswestin/cockroach,maxlang/cockroach,nieyy/cockroach,veteranlu/cockroach,paperstreet/cockroach,arjun4084346/cockroach,nieyy/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,vivekmenezes/cockroach,marcuswestin/cockroach,il9ue/cockroach,maxlang/cockroach,paperstreet/cockroach,petermattis/cockroach,veteranlu/cockroach,il9ue/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,sunya123/cockroach,cuongdo/cockroach,cuongdo/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,maxlang/cockroach,sunya123/cockroach,vaibhavarora/cockroach,arjun4084346/cockroach,cockroachdb/cockroach