AO upgrade tasks not run by OD Importer

When a site backup is imported using the Confluence OnDemand Importer plugin, no Active Objects upgrade tasks are run.

If the same backup is imported as a site import into a BTF instance (i.e. using the normal restore function), then the upgrade tasks are run as expected.

This was discovered whilst diagnosing CONF-31707. The problem is that the OD Importer plugin runs the import in "incremental" mode, which means the AO settings are not deleted as they normally would be. As such, AO thinks it's already at the latest AO version, even though the data it just imported is not.

The fix for CONF-31707 was to add an import preprocessor which reaches into the plugin settings DAO and manually deletes the AO model version setting corresponding to the Workbox schema. That's a dirty hack. This needs fixing properly, since sooner or later it's going to bite someone else.