Force update block template after 30 seconds

To get new transactions in

src/p2p_server.h

@@ -167,6 +167,7 @@ private:
 	void flush_cache();
 	void download_missing_blocks();
 	void check_zmq();
+	void check_block_template();
 	void update_peer_connections();
 	void update_peer_list();
 	void send_peer_list_request(P2PClient* client, uint64_t cur_time);