**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
payload[dag_id].append({'state': state, 'count': count})
        return wwwutils.json_response(payload)
    @expose('/task_stats', methods=['POST'])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG_RUN),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @provide_session
    def task_stats(self, session=None):
        """Task Statistics"""
        allowed_dag_ids = current_app.appbuilder.sm.get_accessible_dag_ids(g.user)
        if not allowed_dag_ids:
            return wwwutils.json_response({})
        
        selected_dag_ids = {unquote(dag_id) for dag_id in request.form.getlist('dag_ids') if dag_id}
        if selected_dag_ids:
            filter_dag_ids = selected_dag_ids.intersection(allowed_dag_ids)
        else:
            filter_dag_ids = allowed_dag_ids
        running_dag_run_query_result = (
            session.query(DagRun.dag_id, DagRun.execution_date)
            .join(DagModel, DagModel.dag_id == DagRun.dag_id)
            .filter(DagRun.state == State.RUNNING, DagModel.is_active)
        )
        running_dag_run_query_result = running_dag_run_query_result.filter(DagRun.dag_id.in_(filter_dag_ids))
        running_dag_run_query_result = running_dag_run_query_result.subquery('running_dag_run')