**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
"""Show Circles on screen for any error in the Webserver"""
    return render_template(
        'airflow/circles.html', hostname=socket.getfqdn() if conf.getboolean(  
            'webserver',
            'EXPOSE_HOSTNAME',
            fallback=True) else 'redact'), 404
def show_traceback(error):  
    """Show Traceback for a given error"""
    from airflow.utils import asciiart as ascii_
    return render_template(
        'airflow/traceback.html',  
        hostname=socket.getfqdn() if conf.getboolean(
            'webserver',
            'EXPOSE_HOSTNAME',
            fallback=True) else 'redact',
        nukular=ascii_.nukular,
        info=traceback.format_exc() if conf.getboolean(
            'webserver',
            'EXPOSE_STACKTRACE',
            fallback=True) else 'Error! Please contact server admin'), 500
class AirflowBaseView(BaseView):