openshift.ks: Use /root/.ssh and not ~/.ssh

In configure_access_keys_on_broker, use /root/.ssh instead of ~/.ssh because ~
expands to /tmp in kickstarts, and so the rsync keys weren't being copied to
/etc/openshift.

Thanks to Rich Lucente for the report.
Merge pull request #45 from Miciah/openshift.ks-use-slash-root-instead-of-tilde

openshift.ks: Use /root/.ssh and not ~/.ssh