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/security.py
"""
        Delete the given Role
        :param role_name: the name of a role in the ab_role table
        """
        session = self.get_session
        role = session.query(sqla_models.Role).filter(sqla_models.Role.name == role_name).first()
        if role:
            self.log.info("Deleting role '%s'", role_name)
            session.delete(role)
            session.commit()
        else:
            raise AirflowException(f"Role named '{role_name}' does not exist")
    @staticmethod
    def get_user_roles(user=None):
        """
        Get all the roles associated with the user.
        :param user: the ab_user in FAB model.
        :return: a list of roles associated with the user.
        """
        if user is None:
            user = g.user
        if user.is_anonymous:
            public_role = current_app.appbuilder.get_app.config["AUTH_ROLE_PUBLIC"]
            return [current_app.appbuilder.sm.find_role(public_role)] if public_role else []
        return user.roles
    def get_current_user_permissions(self):