Validate sudo RunAsUser/RunAsGroup arguments
    
    FreeIPA SUDO rules use --usercat/--groupcat to specify that rule
    applies to all users or groups. Thus, sudorule-add-runasuser and
    sudorule-add-runasgroup accept specific groups and users and do not
    accept ALL reserved word.
    
    The patch validates user and group passed to these commands and
    reports appropriate errors when these are ALL.
    
    Ticket #1496
    https://fedorahosted.org/freeipa/ticket/1496