We were calling exposay_highlight_surface() inside a wl_list_for_each
loop for a layer, but exposay_highlight_surface() calls activate()
which calls shell_surface_update_layer(), which removes the surface
from its layer and reinserts it, causing an infinite loop.
Call exposay_highlight_surface() outside the for_each to avoid this.
https://bugs.freedesktop.org/show_bug.cgi?id=72404