A CounterVector with status as label may create unnecessary overhead
and using the success case with the empty label value wasn't
easy. It's better to have two seperate counters, one for total number
of calls and one for failed calls.
As discussed during the production readiness review, a metric for the
PVC create operations is useful. The "ephemeral_volume" workqueue
metrics were already added in the initial implementation.
The new code follows the example set by the endpoints controller.