This lets back-config reset values for non-magic ARG_TYPES values to zero.
There are 89 cases of this across openldap+contrib, most of them are ok (default is 0/NULL or the value is a MUST), the following have a non-zero default and would be affected:
All of the above could be fixed by adding a
default parameter in the config table, maybe dropping the
notify field there while we're at it, since it's never been implemented. That's what I intend to do here in the next version of this MR.