subscribe and publish(QoS=0,1,2).

* Conn - connack workable.
* Subscribe workable.
* Publish(QoS=1 or 2) use sync_send_event and returns {ok, MsgId} or ok, after [client - broker] flow finished.
* emqttc:ping/1 returns pong, if broker returns pingresp.
* Change unused valiable Name Val to _Val.