Use oslo_db.sqlalchemy.test_fixtures
Use oslo_db.sqlalchemy.test_fixtures

The change in I25e41fc4103b4eafd3aef2b0a863b2053927edad
makes use of oslo_db.tests.*, which was not the intent of the
deprecations added to oslo_db in
I0163e637ffef6d45d2573ebe29b5438911d01fce.   Make use of the
newer fixtures in oslo_db.sqlalchemy.test_fixtures which is
what was intended to supersede oslo_db.sqlalchemy.test_base.

Change-Id: I67cd8f032cbc4be6469ccb90b9f9a6e552bd963d

openstack/glance,openstack/glance,openstack/glance