**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
single=False)
    @has_dag_access(can_dag_edit=True)
    def action_muldelete(self, items):
        """Multiple delete."""
        self.datamodel.delete_all(items)
        self.update_redirect()
        return redirect(self.get_redirect())
    def process_form(self, form, is_created):
        """Process form data."""
        formdata = form.data
        if formdata['conn_type'] in ['jdbc', 'google_cloud_platform', 'grpc', 'yandexcloud', 'kubernetes']:
            extra = {
                key: formdata[key]
                for key in self.extra_fields if key in formdata}
            form.extra.data = json.dumps(extra)
    def prefill_form(self, form, pk):
        """Prefill the form."""
        try:
            extra_dictionary = json.loads(form.data.get('extra', '{}'))
        except JSONDecodeError:
            extra_dictionary = {}
        if not isinstance(extra_dictionary, dict):
            logging.warning('extra field for %s is not a dictionary', form.data.get('conn_id', '<unknown>'))
            return
        for field in self.extra_fields:
            value = extra_dictionary.get(field, '')
            if value:
                field = getattr(form, field)
                field.data = value
class PoolModelView(AirflowModelView):