Right now, for the `KISTLite` scheduler, the write limit on the outbuf for a channel is set to `INT_MAX`. This is crazy high and will bloat the outbuf if the channel is struggling to send out data on the wire or the socket is stuck. Vanilla scheduler uses the `num_cells_writeable()` method to limit the amount it puts on the outbuf which is 32KB maximum. KIST uses the kernel information for this limit. This is very important that we actually put a limit in the outbuf because it keeps the cells in the circuit queue and that is handled by our OOM in case of memory pressure. I suggest we simply use the `channel_num_cells_writeable()` for the upper limit when KISTLite is used.