relax TestRaftLogQueue
relax TestRaftLogQueue

it previously tested that truncating again did not
change anything, but I do not see a reason for why
not.

Fixes #3666.

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