Explicitly define the FQDN hostname for stream queues

Otherwise they will use the system hostname which is the first part of
the FQDN. More info:
https://github.com/rabbitmq/rabbitmq-website/blob/stream-queue/site/stream.md#advertised-host-port

re https://github.com/rabbitmq/rabbitmq-server/issues/2486

Signed-off-by: Gerhard Lazu <gerhard@lazu.co.uk>

s01/e07/k8s/rabbitmq/stream.yml

@@ -17,8 +17,9 @@ spec:
   persistence:
     storage: 10Gi
   rabbitmq:
-    additionalConfig:
+    additionalConfig: |-
       total_memory_available_override_value = 2GiB
+      stream.advertised_host = stream-rabbitmq-server-0.stream-rabbitmq-headless.default
     additionalPlugins:
       - rabbitmq_stream
   override: