docker-compose exec and docker-compose slow are slow, use docker instead

[alberto56]

This is slow:

docker-compose exec a /bin/bash -c 'echo "hello"'
docker-compose port a 80

This is faster:

A=$(docker-compose ps -q a)
docker exec $A /bin/bash -c 'echo "hello"'
docker post $A 80

[alberto56]

See docker/compose#4748, we could gain some speed here.