Adapt autotest to new expected "Space" key behaviour

The old expected behaviour was that pressing Space would select
the current item. We now trigger selection mode instead and don't
select. At some point in the future we might want to instead have
Space trigger a "QuickLook" feature for quick viewing of full
files. In any case, the old behaviour of having Space select is
no longer expected, but Ctrl+Space can still be used for this.

It might also make sense to have Space trigger the old selection
behaviour if both selection mode and "QuickLook" are disabled, but
that is very low priority and will cause more code complexity than
the non-default benefits are worth.


(cherry picked from commit df5cf6fe)