Introduce systemd upgrade script
    
    As user has no means to recover existing FreeIPA install after
    upgrading from SysV to systemd, introduce upgrade script.
    
    The upgrade script does following:
    - restores symlinks in FreeIPA's Dogtag installation
    - converts FreeIPA directory server instances to systemd
    - converts FreeIPA directory server configuration to be compatible
      with systemd services
    - converts FreeIPA KDC configuration to be compatible
      with systemd services
    - re-enables FreeIPA
    
    Script does nothing if FreeIPA is already active systemd service