Duplicate prometheus metrics when testing/importing hermes, hermes2
Motivation
----------
Importing hermes and hermes2 at the same time now fails in testing, because the prometheus metrics are named the same and are initialized on module import.

The error is:
```
ValueError: Duplicated timeseries in CollectorRegistry: set(['rucio_daemons_hermes_reconnect_total', 'rucio_daemons_hermes_reconnect_created'])
```

which is caused on this line:
https://github.com/rucio/rucio/blob/a4ea2cf45961641e9f266f07fefc0a8e8be96498/lib/rucio/daemons/hermes/hermes2.py#L73

See the checks on PR https://github.com/rucio/rucio/pull/3947


Modification
------------
Move initialization to the `run` Method
diff --git a/lib/rucio/daemons/hermes/hermes2.py b/lib/rucio/daemons/hermes/hermes2.py
index dc19a3229..e66463883 100644
--- a/lib/rucio/daemons/hermes/hermes2.py
+++ b/lib/rucio/daemons/hermes/hermes2.py
@@ -70,7 +70,7 @@ logging.basicConfig(stream=sys.stdout,
 
 GRACEFUL_STOP = threading.Event()
 
-RECONNECT_COUNTER = Counter('rucio_daemons_hermes_reconnect', 'Counts Hermes reconnects to different ActiveMQ brokers', labelnames=('host',))
+RECONNECT_COUNTER = Counter('rucio_daemons_hermes2_reconnect', 'Counts Hermes2 reconnects to different ActiveMQ brokers', labelnames=('host',))
 
 
 def default(datetype):
['lib/rucio/daemons/hermes/hermes2.py']