MINOR: mux-quic: use send-list for immediate sending retry

Sending is done with several iterations over qcs streams in qc_send().
The first loop is conducted over streams in <qcc.send_list>. After this
first iteration, some streams may still have data in their Tx buffer but
were blocked by a full qc_stream_desc buffer. In this case, they have
release their qc_stream_desc buffer in qcc_streams_sent_done().

New iterations can be done for these streams which can allocate new
qc_stream_desc buffer if available. Before this patch, this was done
through another stream list <qcc.send_retry_list>. Now, we can reuse the
new <qcc.send_list> for this usage.

This is safe to use as after first iteration, we have guarantee that
either one of the following is true if there is still streams in
<qcc.send_list> :
* transport layer has rejected data due to congestion
* stream is left because it is blocked on stream flow control
* stream still has data and has released a fulfilled qc_stream_desc
  buffer. Immediate retry is useful for these streams : they will
  allocate a new qc_stream_desc buffer if possible to continue sending.

This must be backported up to 2.7.
1 file changed