xmlrpc test: add test for preserved > stage user
When moving a preserved user to the stage area, check that the
custom attributes are not lost ( = the attr for which there is
no specific user_stage option).
Test scenario:
- add a stage user with --setattr "businesscategory=value"
- activate the user, check that businesscategory is still present
- delete (preserve) the user, check that attr is still present
- stage the user, check that attr is still present
Related: https://pagure.io/freeipa/issue/7597
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>