Adding support for alternative container engines/composition for acc testing

A small side track from MR 1549; as I use podman and not docker, I wanted this to work.

Using these changes, you can use podman and podman compose like this:

CONTAINER_COMPOSE_ENGINE=podman-compose CONTAINER_ENGINE=podman make testacc-up

This will also please people using docker compose and not docker-compose.

This shouldn't break anything as the default still is docker/docker-compose.