**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
)
        try:
            dag = current_app.dag_bag.get_dag(dag_id)
            if dag:
                ti.task = dag.get_task(ti.task_id)
            if response_format == 'json':
                logs, metadata = task_log_reader.read_log_chunks(ti, try_number, metadata)
                message = logs[0] if try_number is not None else logs
                return jsonify(message=message, metadata=metadata)
            metadata['download_logs'] = True
            attachment_filename = task_log_reader.render_log_filename(ti, try_number)
            log_stream = task_log_reader.read_log_stream(ti, try_number, metadata)
            return Response(
                response=log_stream,
                mimetype="text/plain",
                headers={
                    "Content-Disposition": f"attachment; filename={attachment_filename}"
                })
        except AttributeError as e:
            error_message = [
                f"Task log handler does not support read logs.\n{str(e)}\n"
            ]
            metadata['end_of_log'] = True
            return jsonify(message=error_message, error=True, metadata=metadata)
    @expose('/log')
    @has_dag_access(can_dag_read=True)
    @has_access
    @action_logging
    @provide_session
    def log(self, session=None):