input: Unlink saved kbd focus listener when releasing seat
input: Unlink saved kbd focus listener when releasing seat

Not doing this would leave a invalid list item in the view's destroy
signal listener list if destroying a seat that had previously lost
keyboard focus.

Signed-off-by: Jonas Ådahl <67dcd8a17e758192e0cbb577ce1d62cc7da6cf49@gmail.com>

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