Hack to fix issue of switching apps

Hack to fix issue of switching apps

To switching between apps, controlling surface's
visiblity (on/off) does not work as intended.

It looks work well to set render order of layers properly.

TODO: switching between apps and navigation still doesn't
work. For develop, navigation icon is assgined to
'controls@0.1' and now, controls app doesn't make any
wl_surfaces (don't know why). Probably this causes issue
switching between apps <-> navigation.

Signed-off-by: Tadao Tanikawa <tanikawa.tadao@jp.panasonic.com>