This commit is based on https://review.opendev.org/c/openstack/magnum/+/825421
Allow metrics collection for etcd by prometheus.
DependsOn: kubernetes/automation/releases/cern-magnum!90 (merged) Closes: kubernetes/automation/releases/cern-magnum#11 (closed)
Change-Id: I599568dd016e935936d0bc5bf3c9046615dba46b