ipa_range_check: Change range_check return values from int to range_check_result_t enum
    
    Using integers for return values that are used for complex casing can be fragile
    and typo-prone. Change range_check function to return range_check_result_t enum,
    whose values properly describes each of the range_check results.
    
    Part of: https://fedorahosted.org/freeipa/ticket/4137
    
    Reviewed-By: Martin Kosek <mkosek@redhat.com>