Remove orphaned flavors

Currently, when a resource class is deleted, the
associated tuskar flavors are not deleted.  This is
problematic, especially because ids are re-used,
creating unintended associations between new
resource classes and old flavors.

This patch removes the tuskar flavors from the database.

Partial-Bug: #1233267
Change-Id: I3d0046ba927faf095e3a66ccb538270c78745228

tuskar/db/sqlalchemy/api.py

@@ -466,6 +466,9 @@ class Connection(api.Connection):
             session.query(models.Rack).filter_by(
                 resource_class_id=resource_class_id
             ).update({"resource_class_id": None})
+            session.query(models.Flavor).filter_by(
+                resource_class_id=resource_class_id
+            ).delete()
             session.query(models.ResourceClass
                           ).filter_by(id=resource_class_id).delete()
             session.commit()