Update download_command to work with latest LAVA

LAVA version 2021.11 introduces a change in the way paths in compressed
overlays are handled breaking Apertis tests.

Fix the issue by specifying the path to be use to extract the compressed
overlay.

Additional information:

https://gitlab.collabora.com/lava/lava/-/commit/07048f042c65202eb75ac874cc93eabd2d96cd54



Signed-off-by: Walter Lozano <walter.lozano@collabora.com>