shell: Tidy up unset_fullscreen()
shell: Tidy up unset_fullscreen()

No functional changes, merely some presentational cleanup.

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