Fix memory limits in docker-compose to use strings, not numbers
    
    docker-compose with commit https://github.com/docker/compose/commit/2b4d409ac3da2096c43284e262f2b0c1b66c488b
    started to require memory limits to be specified as strings.
    
    Related: https://pagure.io/freeipa/issue/8494
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>