nixos/tests/containers-imperative: Fix test

Make sure that we always have everything available within the store of
the VM, so let's evaluate/build the test container fully on the host
system and propagate all dependencies to the VM.

This way, even if there are additional default dependencies that come
with containers in the future we should be on the safe side as these
dependencies should now be included for the test as well.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Cc: @kampfschlaefer, @edolstra