func (r *raftState) getLastIndex() uint64 {
	r.lastLock.Lock()
	defer r.lastLock.Unlock()
	return max(r.lastLogIndex, r.lastSnapshotIndex)
}
func (r *raftState) getLastIndex() uint64 {
	r.lastLock.Lock()
	defer r.lastLock.Unlock()
	return max(r.lastLogIndex, r.lastSnapshotIndex)
}
// getLastIndex returns the last index in stable storage.
// Either from the last log or from the last snapshot.