This has support for disabling metrics_collector, as captured in
rabbitmq/rabbitmq-management-agent#78 & rabbitmq/rabbitmq-management#691
Since we want management to be enabled, this doesn't help our use-case,
but this option is perfect for users that want metrics, but don't want
to pay the overhead of Management - especially metric aggregations.
[#164376052]
Gerhard Lazu