sched: channel_more_to_flush() is probably looking at the wrong queue

In the scheduler (both vanilla and kist), we do flush cells from the outgoing_queue to the outbuf using channel_flush_some_cells().

However, once we are done and to know what state the channel should be in, we use channel_more_to_flush() that looks at two things, the incoming_queue and the number of cells in the cmux.

It seems from my investigation that tor doesn't have this concept of "flushing cells from the incoming queue" so it doesn't make sense to look at it when we are trying to flush cells from the outgoing_queue to the outbuf so we can actually send() them.

Thus, this function should look at the outgoing_queue in my opinion although if I'm right in legacy/trac#23709 (moved), all this could change.