When the first boot fails for some reason and the host keys files
are created, but the content not synced into the disk, during the
second boot, the keygen is not run, but the sshd will not start.
Changing condition mitigates this case.
Split out the host keygen into their own command, to ease future migration
to systemd. Compatitbility with the init script was kept.
Migrate the package to full native systemd unit files, according to the Fedora
packaging guidelines.
Prepate the unit files for running an ondemand server. (do not add it actually)
