Add libselinux-python to the ansible-node group
    
    If the target system has SELinux present, we need to make sure
    that we have libselinux-python available or else nearly all Ansible
    modules will fail with the error "Aborting, target uses selinux but
    python bindings (libselinux-python) aren't installed!"
    
    Resolves: RHBZ#1374491
    
    Signed-off-by: Stephen Gallagher <sgallagh@redhat.com>