**Apache Airflow version**: 2.1.0

**Browsers**: Chrome and Firefox

**What happened**:

Before upgrading to 2.1.0

![before](https://user-images.githubusercontent.com/14293802/120359517-c1ca1100-c2d5-11eb-95ba-58ccc0a3ac37.png)

After upgrading to 2.1.0

![after](https://user-images.githubusercontent.com/14293802/120359528-c4c50180-c2d5-11eb-8e04-f34846ea2736.png)

**What you expected to happen**:

Show/Edit/Delete under Security -> Users are available

<!-- What do you think went wrong? -->

**How to reproduce it**:

Go to Security -> Users (as an admin of course) 
airflow/www/views.py
dag_id,
        task_id,
        origin,
        execution_date,
        upstream,
        downstream,
        future,
        past,
        state,
    ):
        dag = current_app.dag_bag.get_dag(dag_id)
        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")
            return redirect(origin)
        execution_date = timezone.parse(execution_date)
        altered = dag.set_task_instance_state(
            task_id, execution_date, state, upstream=upstream, downstream=downstream, future=future, past=past
        )
        flash(f"Marked {state} on {len(altered)} task instances")
        return redirect(origin)
    @expose('/confirm', methods=['GET'])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def confirm(self):