Remove manual host registration

Removing manual host registration capabilities from installer, because
currently end to end workflow with successful deployment of
non-provisioned hosts is not possible. To implement the feature end to
end later, we need to:

* revert this commit of staypuft-installer

* make staypuft-client-installer report the discovery facts (can be
  done by running the registration puppet with FACTER_LIB env variable
  set to a dir where the extra facts file [1] resides)

* update staypuft-register-host command to use
  staypuft-client-installer on the target machine

* make staypuft work with non-managed nodes

[1] https://github.com/theforeman/foreman-discovery-image/blob/ebbdda2547da1c809caaaa76d7fe63c4f81a9cea/root/usr/share/fdi/facts/discovery-facts.rb