ipa_range_check: Use special attributes to determine presence of RID bases
The slapi_entry_attr_get_ulong which is used to get value of the RID base
attributes returns 0 in case the attribute is not set at all. We need
to distinguish this situation from the situation where RID base attributes
are present, but deliberately set to 0.
Otherwise this can cause false negative results of checks in the range_check
Part of: https://fedorahosted.org/freeipa/ticket/4137
Reviewed-By: Alexander Bokovoy <email@example.com>