Add discover packet.
Add discover packet.

lu-zero/aravis,AnilRamachandran/aravis,AnilRamachandran/aravis,AravisProject/aravis,AnilRamachandran/aravis,AravisProject/aravis,lu-zero/aravis,AravisProject/aravis,AnilRamachandran/aravis,lu-zero/aravis,AravisProject/aravis,AnilRamachandran/aravis,AravisProject/aravis,lu-zero/aravis,lu-zero/aravis