**Apache Airflow version**:

master

**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**: breeze

**What happened**:

This DAG
```python
from airflow import models
from airflow.operators.dummy_operator import DummyOperator
from airflow.utils.dates import days_ago

with models.DAG("test", start_date=days_ago(1), schedule_interval=None,) as dag:
    t1 = DummyOperator(task_id="t1")
    t2 = DummyOperator(task_id="t2")
    t1 >> t2
```

is rendering like that:

<img width="1374" alt="Screenshot 2020-08-27 at 19 59 41" src="https://user-images.githubusercontent.com/9528307/91478403-11d7fb00-e8a0-11ea-91d0-d7d578bcb5a2.png">

**What you expected to happen**:

I expect to see same relations as defined in DAG file

**How to reproduce it**:

Render the example DAG from above.


**Anything else we need to know**:

I'm surprised by this bug 👀 

airflow/www/views.py
commit=False)
        details = "\n".join([str(t) for t in to_be_altered])
        response = self.render_template(
            "airflow/confirm.html",
            message=("Here's the list of task instances you are about to mark as {}:".format(state)),
            details=details)
        return response
    @expose('/failed', methods=['POST'])
    @has_dag_access(can_dag_edit=True)
    @has_access
    @action_logging
    def failed(self):
        """Mark task as failed."""
        dag_id = request.form.get('dag_id')
        task_id = request.form.get('task_id')
        origin = get_safe_url(request.form.get('origin'))
        execution_date = request.form.get('execution_date')
        confirmed = request.form.get('confirmed') == "true"
        upstream = request.form.get('failed_upstream') == "true"
        downstream = request.form.get('failed_downstream') == "true"
        future = request.form.get('failed_future') == "true"
        past = request.form.get('failed_past') == "true"
        return self._mark_task_instance_state(dag_id, task_id, origin, execution_date,
                                              confirmed, upstream, downstream,
                                              future, past, State.FAILED)
    @expose('/success', methods=['POST'])
    @has_dag_access(can_dag_edit=True)
    @has_access
    @action_logging
    def success(self):