add tests for sssd container install/run

[miabbott]

In the most recent RHELAH release, we got bit by a bug (RHBZ #1454292) where the sssd container would not start when using the atomic run command.

We should add a check to the improved-sanity-test that we can use atomic install and atomic run with the sssd container. I think we can do this for only the HEAD version.

This would enable regular testing of the container on our continuous streams where atomic is built from git master.

[miabbott]

(3) Add [a-h-t] sanity test for sssd container with atomic install/run