#20 ZMQ Network disturbing

[Shuqi Dai]

commit [r527]

Network disturbing
[Description] the midi_player still received and processed the messages from the conductor and get stuck when it was .not in ‘Conductor’ Mode
[Solution] add message_ignore variable to observing mode switching.
ignore the messages received when we are not in conductor mode.
[Modification] in mp_net.srp