BUG/MINOR: mux-h1: Fix handling of 408-Request-Time-Out

When a timeout is detected waiting for the request, a 408-Request-Time-Out
response is sent. However, an error was introduced by commit 6858d76cd3
("BUG/MINOR: mux-h1: Obey dontlognull option for empty requests"). Instead
of inhibiting the log message, the option was stopping the error sending.

Of course, we must do the opposite.

This patch must be backported as far as 2.4.
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 15abff3..55b5ca4 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -2749,9 +2749,10 @@
 		_HA_ATOMIC_INC(&sess->listener->counters->failed_req);
 
 	h1c->errcode = 408;
+	ret = h1_send_error(h1c);
 	if (b_data(&h1c->ibuf) || !(sess->fe->options & PR_O_NULLNOLOG))
-		ret = h1_send_error(h1c);
-	sess_log(sess);
+		sess_log(sess);
+
   end:
 	return ret;
 }