SIMPLE: Fail on any error parsing the access control list
    
    Luckily this error was hidden by the fact that SSSD didn't start at all
    when an unparseable name was encountered after startup. Otherwise, this
    would have been a security issue.
    
    Nonetheless, we should just fail and deny access if we can't parse a
    name in a simple access list.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>