p11: add PKCS11_LOGIN_TOKEN_NAME environment variable
    
    The PKCS11_LOGIN_TOKEN_NAME environment variable is e.g. used by the
    Gnome Settings Daemon to determine the name of the token used for login.
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    (cherry picked from commit d86224608ff60ec5cc7e7cbf9e53d8a04e083530)