Followup smp fix

For some time a have added followup moves in the movepicker. Now i have seen a bug if the smp race condition is triggered. Under this condition the last move from the 'killer'-list is removed. But If the followup move but it is not used because it matched with a counter or killer move than the last counter (or even killler move if no countermove was found) is removed. This fix triggers the smp race condition only if a followup move is really added.