Cloned from: https://pagure.io/freeipa/issue/9370

FreeIPA KDB driver stores and allows to retrieve a master key used by the Kerberos realm.  This functionality is implemented with `ipadb_fetch_master_key()` and `ipadb_store_master_key_list()` but they assume there is only one key stored (to be stored). Additionally, KDB driver does not provide `fetch_master_key_list()` (none of the in-tree krb5 KDB drivers provide a sensible version either).

Storing more than one master key is needed to allow migration to a different encryption type.