**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
"""Filter using DagIDs"""
    def apply(self, query, func): 
        if current_app.appbuilder.sm.has_all_dags_access():
            return query
        filter_dag_ids = current_app.appbuilder.sm.get_accessible_dag_ids()
        return query.filter(self.model.dag_id.in_(filter_dag_ids))
class AirflowModelView(ModelView):  
    """Airflow Mode View."""
    list_widget = AirflowModelListWidget
    page_size = PAGE_SIZE
    CustomSQLAInterface = wwwutils.CustomSQLAInterface
class SlaMissModelView(AirflowModelView):
    """View to show SlaMiss table"""
    route_base = '/slamiss'
    datamodel = AirflowModelView.CustomSQLAInterface(SlaMiss)  
    base_permissions = ['can_list']
    list_columns = ['dag_id', 'task_id', 'execution_date', 'email_sent', 'timestamp']
    add_columns = ['dag_id', 'task_id', 'execution_date', 'email_sent', 'timestamp']
    edit_columns = ['dag_id', 'task_id', 'execution_date', 'email_sent', 'timestamp']
    search_columns = ['dag_id', 'task_id', 'email_sent', 'timestamp', 'execution_date']
    base_order = ('execution_date', 'desc')
    base_filters = [['dag_id', DagFilter, lambda: []]]
    formatters_columns = {
        'task_id': wwwutils.task_instance_link,
        'execution_date': wwwutils.datetime_f('execution_date'),
        'timestamp': wwwutils.datetime_f('timestamp'),
        'dag_id': wwwutils.dag_link,
    }
class XComModelView(AirflowModelView):