**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
if type(attr) != type(self.task):  
                    ti_attrs.append((attr_name, str(attr)))
        task_attrs = []
        for attr_name in dir(task):
            if not attr_name.startswith('_'):
                attr = getattr(task, attr_name)
                
                if type(attr) != type(self.task) and \
                        attr_name not in wwwutils.get_attr_renderer():  
                    task_attrs.append((attr_name, str(attr)))
                
        
        special_attrs_rendered = {}
        for attr_name in wwwutils.get_attr_renderer():
            if hasattr(task, attr_name):
                source = getattr(task, attr_name)
                special_attrs_rendered[attr_name] = \
                    wwwutils.get_attr_renderer()[attr_name](source)
        no_failed_deps_result = [(
            "Unknown",
            "All dependencies are met but the task instance is not running. In most "
            "cases this just means that the task will probably be scheduled soon "
            "unless:<br/>\n- The scheduler is down or under heavy load<br/>\n{}\n"
            "<br/>\nIf this task instance does not start soon please contact your "
            "Airflow administrator for assistance.".format(
                "- This task instance already ran and had it's state changed manually "
                "(e.g. cleared in the UI)<br/>" if ti.state == State.NONE else ""))]
        
        dep_context = DepContext(SCHEDULER_QUEUED_DEPS)
        failed_dep_reasons = [(dep.dep_name, dep.reason) for dep in