The function most_nd_stop is only called by successful return from the
function most_nd_open, so the channels_opened is always true in the
function most_nd_stop.
The functions aim_resume_tx_channel and aim_rx_data are only called
after successful most_start_channel in the function most_nd_open, so the
channels_opened is always true in the functions aim_resume_tx_channel
and aim_rx_data.