Add a Requires on openssh-clients
Generally when you have `ansible` you really want the real `ssh`, otherwise
it may fall back to paramiko which doesn't work in a whole lot of scenarios.
Specifically I was trying to use this inside a container for libostree
testing and it took me quite a while to debug this missing dep:
https://github.com/ostreedev/ostree/pull/1462#issuecomment-369048441