Suggestion: Install SSH client for r10k

[blueback13]

Git and r10k are installed when building the Puppet server docker image, but no SSH client is included. This means that r10k can only be used with HTTPS repositories.

There are two options to enable SSH clients:

1. Install openssh-client with the other dependency packages
2. Install the rugged gem when r10k is installed
3. Or install both openssh-client and rugged

[rwaffen]

@voxpupuli/tools-containerimages guys, what do you think? adding git, rugged or both, what's best?

[bastelfreak]

both have different benefits, so I think we should include both