Get block height and consensus hash.  Try the cache, and
        on cache miss, fetch from the db

def get_consensus_info(self):
        """
        Get block height and consensus hash.  Try the cache, and
        on cache miss, fetch from the db
        """
        cached_consensus_info = self.get_cached_consensus_info()
        if cached_consensus_info:
            return cached_consensus_info

        db = get_db_state(self.working_dir)
        ch = db.get_current_consensus()
        block = db.get_current_block()
        db.close()

        cinfo = {'consensus_hash': ch, 'block_height': block}
        self.set_cached_consensus_info(cinfo)
        return cinfo