Change group.waitForCallback to a counter
Change group.waitForCallback to a counter

I don't know exactly what happened inside Raft, but when I ran
TestRemoveLeader in multiraft_test.go, there was a writeResponse
that contains two committed ConfChanges (one for adding new node 4 and the
other for removing node 0). The writeResponse itself was sent the
newly added node 4.

To handle such a case correctly, group.waitForCallback needs to be a
count, not a bool.

marcuswestin/cockroach,petermattis/cockroach,arjun4084346/cockroach,glycerine/cockroach,arjun4084346/cockroach,glycerine/cockroach,jamesgraves/cockroach,jess-edwards/cockroach,nieyy/cockroach,jmank88/cockroach,glycerine/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,sunya123/cockroach,vaibhavarora/cockroach,il9ue/cockroach,mbertschler/cockroach,cockroachdb/cockroach,jmank88/cockroach,cockroachdb/cockroach,linearb/cockroach,cuongdo/cockroach,cuongdo/cockroach,sunya123/cockroach,petermattis/cockroach,mbertschler/cockroach,maxlang/cockroach,maxlang/cockroach,paperstreet/cockroach,mbertschler/cockroach,bg451/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,bg451/cockroach,jamesgraves/cockroach,jamesgraves/cockroach,petermattis/cockroach,veteranlu/cockroach,jess-edwards/cockroach,sunya123/cockroach,jmank88/cockroach,paperstreet/cockroach,arjun4084346/cockroach,linearb/cockroach,nieyy/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,marcuswestin/cockroach,marcuswestin/cockroach,cockroachdb/cockroach,il9ue/cockroach,paperstreet/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,mbertschler/cockroach,jmank88/cockroach,linearb/cockroach,sunya123/cockroach,cockroachdb/cockroach,cuongdo/cockroach,petermattis/cockroach,marcuswestin/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,nieyy/cockroach,jess-edwards/cockroach,jmank88/cockroach,jess-edwards/cockroach,jamesgraves/cockroach,cuongdo/cockroach,vaibhavarora/cockroach,jmank88/cockroach,il9ue/cockroach,veteranlu/cockroach,cockroachdb/cockroach,bg451/cockroach,glycerine/cockroach,marcuswestin/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,petermattis/cockroach,nieyy/cockroach,paperstreet/cockroach,marcuswestin/cockroach,veteranlu/cockroach,bg451/cockroach,il9ue/cockroach,linearb/cockroach,arjun4084346/cockroach,sunya123/cockroach,sunya123/cockroach,arjun4084346/cockroach,jess-edwards/cockroach,linearb/cockroach,marcuswestin/cockroach,jmank88/cockroach,sunya123/cockroach,jess-edwards/cockroach,mbertschler/cockroach,vaibhavarora/cockroach,bg451/cockroach,veteranlu/cockroach,vaibhavarora/cockroach,bg451/cockroach,paperstreet/cockroach,maxlang/cockroach,il9ue/cockroach,vaibhavarora/cockroach,cuongdo/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,nieyy/cockroach,nieyy/cockroach,arjun4084346/cockroach,veteranlu/cockroach,mbertschler/cockroach,petermattis/cockroach,linearb/cockroach,veteranlu/cockroach,jamesgraves/cockroach,mbertschler/cockroach,linearb/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,jamesgraves/cockroach,vaibhavarora/cockroach,il9ue/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,sunya123/cockroach,il9ue/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,maxlang/cockroach,jamesgraves/cockroach,maxlang/cockroach,il9ue/cockroach,cockroachdb/cockroach,petermattis/cockroach,glycerine/cockroach,maxlang/cockroach,vaibhavarora/cockroach,petermattis/cockroach,maxlang/cockroach,glycerine/cockroach,nieyy/cockroach,marcuswestin/cockroach,vivekmenezes/cockroach,jess-edwards/cockroach,bg451/cockroach,nieyy/cockroach,cuongdo/cockroach,glycerine/cockroach