MEDIUM: connection: only call the data->wake callback on activity

MEDIUM: connection: only call the data->wake callback on activity

We now check the connection flags for changes in order not to call the
data->wake callback when there is no activity. Activity means a change
on any of the CO_FL_*_SH, CO_FL_ERROR, CO_FL_CONNECTED, CO_FL_WAIT_CONN*
flags, as well as a call to data->recv or data->send.