
**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
"""Timer metric that can be cancelled"""
        if stat and self.allow_list_validator.test(stat):
            tags = tags or []
            return Timer(self.dogstatsd.timer(stat, *args, tags=tags, **kwargs))
        return Timer()
class _Stats(type):
    instance: Optional[StatsLogger] = None
    def __getattr__(cls, name):
        return getattr(cls.instance, name)
    def __init__(cls, *args, **kwargs):
        super().__init__(cls)
        if cls.__class__.instance is None:
            try:
                is_datadog_enabled_defined = conf.has_option('metrics', 'statsd_datadog_enabled')
                if is_datadog_enabled_defined and conf.getboolean('metrics', 'statsd_datadog_enabled'):
                    cls.__class__.instance = cls.get_dogstatsd_logger()
                elif conf.getboolean('metrics', 'statsd_on'):
                    cls.__class__.instance = cls.get_statsd_logger()
                else:
                    cls.__class__.instance = DummyStatsLogger()
            except (socket.gaierror, ImportError) as e:
                log.error("Could not configure StatsClient: %s, using DummyStatsLogger instead.", e)
                cls.__class__.instance = DummyStatsLogger()
    @classmethod
    def get_statsd_logger(cls):