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
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import collections
import copy
import itertools
import json
import logging
import math
import re
import socket
import sys
import traceback
from collections import defaultdict
from datetime import timedelta
from json import JSONDecodeError
from operator import itemgetter
from typing import Iterable, List, Optional, Tuple
from urllib.parse import parse_qsl, unquote, urlencode, urlparse
import lazy_object_proxy
import markupsafe
import nvd3
import sqlalchemy as sqla
from flask import (
    Markup,
    Response,
    abort,
    before_render_template,
    current_app,