Airflow 2.1.0, Docker

**What happened**:

Users with the Guest role assigned are stuck in a redirect loop once they attempt to login successfully to the web interface.

**What you expected to happen**:

Get minimal access to the dashboard with the appropriate views for a guest role

**How to reproduce it**:
1. Assign a guest role to any user and remove any other roles with the administrator user.
2. Logout from the admin account 
3. Login as the guest user
4. You will notice constant HTTP redirects, and the dashboard will not show up.


airflow/www/views.py
tags = [
                {"name": name, "selected": bool(arg_tags_filter and name in arg_tags_filter)}
                for name, in dagtags
            ]
            import_errors = session.query(errors.ImportError).order_by(errors.ImportError.id).all()
        if import_errors:
            dag_filenames = {dag.fileloc for dag in dags}
            all_dags_readable = (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG) in user_permissions
            for import_error in import_errors:
                if all_dags_readable or import_error.filename in dag_filenames:
                    flash(
                        "Broken DAG: [{ie.filename}] {ie.stacktrace}".format(ie=import_error),
                        "dag_import_error",
                    )
        from airflow.plugins_manager import import_errors as plugin_import_errors
        for filename, stacktrace in plugin_import_errors.items():
            flash(
                f"Broken plugin: [{filename}] {stacktrace}",
                "error",
            )
        num_of_pages = int(math.ceil(num_of_all_dags / float(dags_per_page)))
        state_color_mapping = State.state_color.copy()
        state_color_mapping["null"] = state_color_mapping.pop(None)
        page_title = conf.get(section="webserver", key="instance_name", fallback="DAGs")
        return self.render_template(
            'airflow/dags.html',
            dags=dags,
            current_page=current_page,
            search_query=arg_search_query if arg_search_query else '',
            page_title=page_title,