django/backends: Handle error when user session is no longer active

When a user session has been terminated without using the logout view
(for instance a user can logout from all its authenticated sessions
using the Keycloak account UI), the expired OIDC profile is still
in webapp cache which causes errors and prevent new user logins.

So ensure to remove expired profile from cache when detecting Keycloak
session is no longer active in django authentication backend.

Related to T3496