Increase collect_statistics_interval (#643)

https://www.rabbitmq.com/prometheus.html#prometheus:
"For production systems, we recommend a minimum value of 15s for
Prometheus scrape interval and a 10000 (10s) value for RabbitMQ's
collect_statistics_interval. With these values, Prometheus doesn't
scrape RabbitMQ too frequently, and RabbitMQ doesn't update metrics
unnecessarily."

The previous collect_statistics_interval was 5000 (5s).

Author: ansd

docs/examples/production-ready/rabbitmq.yaml

@@ -16,6 +16,7 @@ spec:
       cluster_partition_handling = pause_minority
       vm_memory_high_watermark_paging_ratio = 0.99
       disk_free_limit.relative = 1.0
+      collect_statistics_interval = 10000
   persistence:
     storageClassName: ssd
     storage: "500Gi"