Allow rename of a host group
    
    RN: host groups can now be renamed with IPA CLI:
    RN: 'ipa hostgroup-mod group-name --rename new-name'.
    RN: Protected hostgroups ('ipaservers') cannot be renamed.
    
    Fixes: https://pagure.io/freeipa/issue/6783
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>