In the Openfire 4.3.1 was announced a new feature - one-time access tokens (https://issues.igniterealtime.org/browse/OF-1285 and https://github.com/igniterealtime/Openfire/pull/1249) which used for recovery purposes.
The openfire.xml was changed with comments to describe about this feature. And the same file was changed during installation. Therefore apt don’t know what it should do. You can ignore changes and choose the ‘N’ choice to save your configuration.