Ticket #47431 - Duplicate values for the attribute nsslapd-pluginarg are not handled correctly
    
    Fix description: Added the attributes nsslapd-pluginarg0 to
    nsslapd-pluginarg15 in the schema file with the condition that
    they must be singlevalued. This solves the issue of incorrect
    handling of duplicate and multiple values of these attributes.
    This fix also solves the problem of non-continuous numbers in
    the nsslapd-pluginarg attributes and makes them continuous if
    they are not.
    
    https://fedorahosted.org/389/ticket/47431
    
    Reviewed by nhosoi.