desktop-shell: Make set_toplevel() clear surface states
desktop-shell: Make set_toplevel() clear surface states

This is used from wl_shell and xwayland and we need to make sure
xwayland also gets this behavior.

jonnylamb/weston,Fantu/compositor-spice,udoprog/weston,giucam/weston,krezovic/weston,eyolfson/weston,kwm81/weston,krezovic/weston,xorgy/weston,Tarnyko/weston-xdg_surface_present,Tarnyko/weston-xdg_surface_present,mchalupa/weston,Gnurou/weston,Fantu/compositor-spice,mchalupa/weston,sir-murray/weston,udoprog/weston,kwm81/weston,eyolfson/weston,sir-murray/weston,xorgy/weston,Fantu/compositor-spice,jonnylamb/weston,Gnurou/weston,giucam/weston