Register metrics exposed by sig-storage-lib

[RaunakShah]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR registers metrics exposed by sig-storage-lib in the external provisioner.
After this change, querying the http endpoint includes the following metrics:

1. Create an nginx pod in the cluster

2. Get the IP address of the Pod running csi-provisioner

% kubectl get pod -o wide
NAME                   READY   STATUS    RESTARTS   AGE     IP            NODE              NOMINATED NODE   READINESS GATES
csi-hostpath-socat-0   1/1     Running   0          31h     10.244.1.6    csi-prow-worker   <none>           <none>
csi-hostpathplugin-0   8/8     Running   0          5h47m   10.244.1.23   csi-prow-worker   <none>           <none>
nginx                  1/1     Running   0          9h      10.244.1.18   csi-prow-worker   <none>           <none>

3. Exec into the nginx pod and curl the metrics endpoint

% kubectl exec -it nginx -- sh
# curl 10.244.1.23:8080/metrics
# HELP controller_persistentvolume_delete_duration_seconds Latency in seconds to delete persistent volumes. Failed deletion attempts are ignored. Broken down by storage class name.
# TYPE controller_persistentvolume_delete_duration_seconds histogram
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.005"} 0
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.01"} 0
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.025"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.05"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.1"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.25"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="0.5"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="1"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="2.5"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="5"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="10"} 1
controller_persistentvolume_delete_duration_seconds_bucket{class="csi-hostpath-sc",le="+Inf"} 1
controller_persistentvolume_delete_duration_seconds_sum{class="csi-hostpath-sc"} 0.011995
controller_persistentvolume_delete_duration_seconds_count{class="csi-hostpath-sc"} 1
# HELP controller_persistentvolume_delete_total Total number of persistent volumes deleted succesfully. Broken down by storage class name.
# TYPE controller_persistentvolume_delete_total counter
controller_persistentvolume_delete_total{class="csi-hostpath-sc"} 1
# HELP controller_persistentvolumeclaim_provision_duration_seconds Latency in seconds to provision persistent volumes. Failed provisioning attempts are ignored. Broken down by storage class name.
# TYPE controller_persistentvolumeclaim_provision_duration_seconds histogram
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.005"} 0
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.01"} 0
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.025"} 0
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.05"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.1"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.25"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="0.5"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="1"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="2.5"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="5"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="10"} 1
controller_persistentvolumeclaim_provision_duration_seconds_bucket{class="csi-hostpath-sc",le="+Inf"} 1
controller_persistentvolumeclaim_provision_duration_seconds_sum{class="csi-hostpath-sc"} 0.032850625
controller_persistentvolumeclaim_provision_duration_seconds_count{class="csi-hostpath-sc"} 1
# HELP controller_persistentvolumeclaim_provision_total Total number of persistent volumes provisioned succesfully. Broken down by storage class name.
# TYPE controller_persistentvolumeclaim_provision_total counter
controller_persistentvolumeclaim_provision_total{class="csi-hostpath-sc"} 1
...

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Register metrics exposed by sig-storage-lib

[xing-yang]

In the output, please also include the command you run that generated the results.

[xing-yang]

/assign @jsafrane

[RaunakShah]

In the output, please also include the command you run that generated the results.

Done, added the exact test steps!

[jsafrane]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jsafrane, RaunakShah

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