enforce timestamp set for all cmds entering Store.Send
enforce timestamp set for all cmds entering Store.Send

otherwise, TestStoreRangeRebalance encounters rare failures:
- lease gets obtained by range X on store Y
- that range gets removed
- lease active, and no request can succeed because the check
  uses the zero timestamp

of course that is just one manifestation of the more general issue.

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