BUG/MINOR: mux-h2/traces: bring back the lost "rcvd H2 REQ" trace

Since commit 7d013e796 ("BUG/MEDIUM: mux-h2: Xfer rxbuf to the upper
layer when creating a front stream"), the rxbuf is lost during the
call to h2c_frt_stream_new(), so the trace that happens later cannot
find a request there and we've lost the useful part indicating what
the request looked like. Let's move the trace before this call.

This should be backported to 2.4.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 1150660..e09b0d9 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -2698,6 +2698,8 @@
 		goto send_rst;
 	}
 
+	TRACE_USER("rcvd H2 request  ", H2_EV_RX_FRAME|H2_EV_RX_HDR|H2_EV_STRM_NEW, h2c->conn, 0, &rxbuf);
+
 	/* Note: we don't emit any other logs below because ff we return
 	 * positively from h2c_frt_stream_new(), the stream will report the error,
 	 * and if we return in error, h2c_frt_stream_new() will emit the error.
@@ -2730,7 +2732,6 @@
 	if (h2s->id > h2c->max_id)
 		h2c->max_id = h2s->id;
 
-	TRACE_USER("rcvd H2 request  ", H2_EV_RX_FRAME|H2_EV_RX_HDR|H2_EV_STRM_NEW, h2c->conn, 0, &rxbuf);
 	return h2s;
 
  conn_err: