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
"""Show confirmation page for marking tasks as success or failed."""
        args = request.args
        dag_id = args.get('dag_id')
        task_id = args.get('task_id')
        execution_date = args.get('execution_date')
        state = args.get('state')
        upstream = to_boolean(args.get('upstream'))
        downstream = to_boolean(args.get('downstream'))
        future = to_boolean(args.get('future'))
        past = to_boolean(args.get('past'))
        try:
            dag = current_app.dag_bag.get_dag(dag_id)
        except airflow.exceptions.SerializedDagNotFound:
            flash(f'DAG {dag_id} not found', "error")
            return redirect(request.referrer or url_for('Airflow.index'))
        try:
            task = dag.get_task(task_id)
        except airflow.exceptions.TaskNotFound:
            flash(f"Task {task_id} not found", "error")
            return redirect(request.referrer or url_for('Airflow.index'))
        task.dag = dag
        if state not in (
            'success',
            'failed',
        ):
            flash(f"Invalid state {state}, must be either 'success' or 'failed'", "error")
            return redirect(request.referrer or url_for('Airflow.index'))
        latest_execution_date = dag.get_latest_execution_date()
        if not latest_execution_date:
            flash(f"Cannot mark tasks as {state}, seem that dag {dag_id} has never run", "error")