In preparation for a switch from docker-compose to docker compose (with
a shim so that docker-compose is docker compose) we switch away from
direct docker exec to using docker-compose exec because the two
different compose implementations use different container names. This
way we shouldn't need to lookup container names at runtime or have
special casing depending on which system we want to use. Instead the
compose runtime will find the correct container to exec in based on the
human readable name in our config file.
Change-Id: I5ffb0007997dfdf2da67df3ada5db4534dc383a7
cab0b13f5c