Fix problem when moving fullscreen window to scratchpad

Fix problem when moving fullscreen window to scratchpad

When moving a fullscreen window to scratchpad with 'move scratchpad', the
focused window would stay fullscreen.

Also, when having a container in fullscreen mode and then focusing a child of
this container and moving it to scratchpad, it would enable fullscreen for
the child window.

This patch fixes both problems, so the scratchpad window is always floating.