If glance is in standalone mode, image import works
fine so enable the tempest tests. Once we will have image
import or other async tasks working with glance under uwsgi
then we can remove this flag and run import tests by default.
Depends-On: https://review.opendev.org/#/c/741425/
Change-Id: I853e8a3815187f0aa8f05c70488ec948a97e55a6