Refs #6013 - Allow modularized policy via DISTRO m4 macro

(cherry picked from commit c325c5fa3daadbb14b3d51e1ec018bea6049c94a)
Add opennebula dependency

(cherry picked from commit bf0cde8a780c5fb7dbd044c7fa3836a7817092e0)
Add foreman_one plugin

(cherry picked from commit e14828300d9e368dbf03f0fc32c659b017583dfc)
Update tito config for 1.6
Update to support RC versions
Release 1.6.0-RC1
Automatic commit of package [foreman] minor release [1.6.0-0.1.RC1].
Automatic commit of package [foreman-proxy] minor release [1.6.0-0.1.RC1].
Automatic commit of package [foreman-installer] minor release [1.6.0-0.1.RC1].
Automatic commit of package [foreman-selinux] minor release [1.6.0-0.1.RC1].