Ensure ssh key config works for libvirt and oci providers

[zabdulre]

The user should be able to specify their ssh key file in their cluster configuration file. This ssh key file should allow users to ssh in to any node that gets created with libvirt or oci. Libvirt currently has a ssh key field - this functionality needs to be validated and confirmed as nominal. Oci does not currently have a ssh key field, this should be added and documented in the man pages.