Detect the database host reservations overwritten by JSON reservations

The host reservations in Kea can be defined in the JSON configuration file or the host database. If the same address is reserved for the same identifier in both places, the JSON configuration entry takes precedence over the database one.

In this case, Stork stores the entry from the database only. It means it isn't possible to inspect the actual reservation used by the Kea daemon or detect duplicated reservations.