Get ids to search for to keep old buckets up to date.

def get_refresh_ids(self):
        """
        Get ids to search for to keep old buckets up to date.
        """
        ids = []
        for bucket in self.router.lonely_buckets():
            rid = random.randint(*bucket.range).to_bytes(20, byteorder='big')
            ids.append(rid)
        return ids