BUG/MEDIUM: stream-int: Don't block SI on a channel policy if EOI is reached

If the end of input is reported by the mux on the conn-stream during a
receive, we leave without evaluating the channel policies. It is especially
important to be able to catch client aborts during server connection
establishment. Indeed, in this case, without this patch, the
stream-interface remains blocked and read events are not forwarded to the
stream. It means it is not possible to detect client aborts.

Thanks to this fix, the abortonclose option should fixed for HAProxy 2.3 and
lower. On 2.4 and 2.5, it seems to work because the stream is created after
the request parsing.

Note that a previous fix of abortonclose option was reverted. This one
should be the right way to fix it. It must carefully be backported as far as
2.0. A observation period on the 2.3 is probably a good idea.

src/stream_interface.c

@@ -1381,6 +1381,14 @@ int si_cs_recv(struct conn_stream *cs)
 		ic->flags |= CF_READ_PARTIAL;
 		ic->total += ret;
 
+		/* End-of-input reached, we can leave. In this case, it is
+		 * important to break the loop to not block the SI because of
+		 * the channel's policies.This way, we are still able to receive
+		 * shutdowns.
+		 */
+		if (cs->flags & CS_FL_EOI)
+			break;
+
 		if ((ic->flags & CF_READ_DONTWAIT) || --read_poll <= 0) {
 			/* we're stopped by the channel's policy */
 			si_rx_chan_blk(si);