migrate-ds: workaround to detect compat tree
Migrate-ds needs to check if compat tree is enabled before
migrating users and groups. The check is doing a base
search on cn=compat,$SUFFIX and considers the compat tree
enabled when the entry exists.
Due to a bug in slapi-nis, the base search may return NotFound
even though the compat tree is enabled. The workaround is to
perform a base search on cn=users,cn=compat,$SUFFIX instead.
Fixes: https://pagure.io/freeipa/issue/8984
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>