Explore integrating some of the tests from Docker Bench for Security into the container-manager

[Toshbrown]

Docker Bench for Security has a number of tests that apply to the security of images, the cmgr could apply the appropriate tests to all app and driver images before they are run on a users databox. for example:

1. Ensure a user for the container has been created (don't run as root)
2. Ensure that containers use trusted base images
3. Ensure unnecessary packages are not installed in the container
4. Ensure Content trust for Docker is Enabled
5. Ensure setuid and setgid permissions are removed in the images
6. Ensure verified packages are only Installed

from https://github.com/docker/docker-bench-security/blob/master/tests/4_container_images.sh would all be useful.