Output handling in the compositor changed, so update the test
accordingly. As a side effect we now send an additional
wl_output.scale event, so have the client handle it.
Also the mapping between wayland's and QImage's format changed
so make it succeed again.

Change-Id: I66d32725c54d93ca1512a6a0ddaf466f58984afc
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>