xwayland: fix fullscreening

set_fullscreen has been sending configure before changing the state
and xwayland windows added border to the fullscreen size.

This fixes the bug:
https://bugs.freedesktop.org/show_bug.cgi?id=83502

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Ryo Munakata <ryomnktml@gmail.com>
Tested-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

desktop-shell/shell.c

@@ -2925,10 +2925,10 @@ shell_interface_set_fullscreen(struct shell_surface *shsurf,
 			       struct weston_output *output)
 {
 	surface_clear_next_states(shsurf);
-	set_fullscreen(shsurf, method, framerate, output);
-
 	shsurf->next_state.fullscreen = true;
 	shsurf->state_changed = true;
+
+	set_fullscreen(shsurf, method, framerate, output);
 }
 
 static int