**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
return redirect(request.referrer or url_for('Airflow.index'))
        execution_date = timezone.parse(execution_date)
        from airflow.api.common.experimental.mark_tasks import set_state
        to_be_altered = set_state(
            tasks=[task],
            execution_date=execution_date,
            upstream=upstream,
            downstream=downstream,
            future=future,
            past=past,
            state=state,
            commit=False,
        )
        details = "\n".join(str(t) for t in to_be_altered)
        response = self.render_template(
            "airflow/confirm.html",
            endpoint=url_for(f'Airflow.{state}'),
            message=f"Here's the list of task instances you are about to mark as {state}:",
            details=details,
        )
        return response
    @expose('/failed', methods=['POST'])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def failed(self):