Trac Ticket #443 - Deleting attribute present in
nsslapd-allowed-to-delete-attrs returns Operations error

https://fedorahosted.org/389/ticket/443

Bug Description: Even if setting a config parameter to nsslapd-
allowed-to-delete-attrs, the value failed to delete if the type
was on|off or integer.

Fix Description: Store all the initial config param values in
ConfigList. If the attribute value is deleted, reset the initial
value.