Called when we discover a zone file.  Queues up a request to reprocess this name's zone files' subdomains.
        zonefile_hash is the hash of the zonefile.
        block_height is the minimium block height at which this zone file occurs.

        This gets called by:
        * AtlasZonefileCrawler (as it's "store_zonefile" callback).
        * rpc_put_zonefiles()

def enqueue_zonefile(self, zonefile_hash, block_height):
        """
        Called when we discover a zone file.  Queues up a request to reprocess this name's zone files' subdomains.
        zonefile_hash is the hash of the zonefile.
        block_height is the minimium block height at which this zone file occurs.

        This gets called by:
        * AtlasZonefileCrawler (as it's "store_zonefile" callback).
        * rpc_put_zonefiles() 
        """
        with self.serialized_enqueue_zonefile:
            log.debug("Append {} from {}".format(zonefile_hash, block_height))
            queuedb_append(self.subdomain_queue_path, "zonefiles", zonefile_hash, json.dumps({'zonefile_hash': zonefile_hash, 'block_height': block_height}))