Undesired `session.expire_all` leads to n+1 in tests

I have covered an endpoint with a test that counts DB queries and reveled n+1 issue.
The n+1 issue is only reproduced in tests so it seems to be related to this line (also if I remove this line the test pass):
https://github.com/jeancochrane/pytest-flask-sqlalchemy/blob/master/pytest_flask_sqlalchemy/fixtures.py#L59

In my app.py, I set following session_options:
```python
db = SQLA(session_options={"autocommit": False, "autoflush": False, "expire_on_commit": False})
```

I guess, `expire_on_commit` option should be considered in the `restart_savepoint` function before expiring all objects.

What do you think?