
**Apache Airflow version**:
2.0.0

**Environment**:

- **OS** (e.g. from /etc/os-release): Ubuntu 20.04 LTS
- **Python version**: 3.8
- **Kernel** (e.g. `uname -a`): x86_64 x86_64 x86_64 GNU/Linux 5.4.0-58-generic #64-Ubuntu
- **Install tools**: pip


**What happened**:

Airflow 2.0 does not send metrics to statsD.

I configure Airflow with official documentation (https://airflow.apache.org/docs/apache-airflow/stable/logging-monitoring/metrics.html) and by this article https://dstan.medium.com/run-airflow-statsd-grafana-locally-16b372c86524 (but I used port 8125). 

I turned on statsD:

```ini
statsd_on = True
statsd_host = localhost
statsd_port = 8125
statsd_prefix = airflow
```

But I do not see airflow metrics at http://localhost:9102/metrics (statsD metrics endpoint).

---

P.S. I noticed this error just using Airflow 2.0. In version 1.10.13 everything is ok in the same environment.

Thank you for advance.



airflow/stats.py
Or without a context manager:
    .. code-block:: python
        timer = Stats.timer().start()
        # Something to time
        frob_the_foos()
        timer.end()
        log.info("Frobbing the foos took %.2f", timer.duration)
    To send a metric:
    .. code-block:: python
        with Stats.timer("foos.frob"):
            # Something to time
            frob_the_foos()
    Or both:
    .. code-block:: python
        with Stats.timer("foos.frob") as t:
            # Something to time
            frob_the_foos()
        log.info("Frobbing the foos took %.2f", t.duration)
    """
    
    
    _start_time: Optional[int]
    duration: Optional[int]
    def __init__(self, real_timer=None):
        self.real_timer = real_timer
    def __enter__(self):
        return self.start()
    def __exit__(self, exc_type, exc_value, traceback):
        self.stop()
    def start(self):