When compositor enters SLEEPING state, the shell plugin goes locked. If
compositor wakes up itself, it will fade in while the shell may not yet
have a lock surface to show.
Fix this by assigning wake-up to be called from the shell, if the
compositor is SLEEPING. The shell may wait for the lock surface request,
and only then wake up the compositor. The compositor will fade in
directly to the lock screen.
krh: original patch for compositor.c
ppaalanen: integration and shell.c changes
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>