wayland: Fix xdg-toplevel and xdg-popup window initialization
Buggy clients can commit the wl_surface several times in a row. On the other hand, XdgToplevelInterface and XdgPopupInterface consider a surface to be initialized if it has been configured. If the second wl_surface commit comes before the configure event is sent, kwin will initialize a toplevel or popup twice, which can trigger asserts.