[Cinder] remove prometheus.io/port
[Cinder] remove prometheus.io/port

This removes the prometheus.io/port from the chart and changes it to
a spec named metrics.
This is related to discussion on slack:

https://operations.global.cloud.sap/docs/support/playbook/kubernetes/target_scraped_multiple_times/#usage-or-prometheusioport-annotation-with-multiple-ports

sapcc/helm-charts,sapcc/helm-charts,sapcc/helm-charts,sapcc/helm-charts