IFP: Fix of limit = 0 (unlimited result)
    
    If we set limit to 0 it means that result is unlimited. Internally we
    restrict number of result by allocation of result array.
    In unlimited case there was a bug and zero array was allocated.
    This fix allocates neccessary array when we know real result size.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/3306
    
    Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>