persistence.volumeName is not used in gitaly chart

Summary

In the values.yaml from gitaly's chart, we can see a parameter volumeName in the persistence part.

This parameter is not used in the volumeClaimTemplates of the statefulset object, so it is difficult to link an existing PV to gitaly.(I test this parameter in the minio chart for example, and it works)

The usecase is mainly if we use a PV with persistenceVolumeReclaimPolicy set to retain.

In that case, if we want reuse the same disk from a previous gitaly instance, we must create manualy a PV and bind it in our new gitaly.

I can submit a fix for this issue

Steps to reproduce

Create manualy a PV in kubernetes, then try to bind it to gitaly statefulset with the param volumeName

Configuration used

• For the PV

kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv-gitlab-gitaly
spec:
  accessModes:
  - ReadWriteOnce
  azureDisk:
    XXXXXXXXXXXXXXXXXXXXXXX
  capacity:
    storage: 50Gi
  persistentVolumeReclaimPolicy: Retain
  storageClassName: azure-disk

in my values.yaml file

gitaly:
  persistence:
    enabled: true
    storageClass: azure-disk
    volumeName: pv-gitlab-gitaly
    accessMode: ReadWriteOnce
    size: 50Gi

Current behavior

volumeName is not use in the statefulset, so I can't use my PV

Expected behavior

volumeName is used in the statefulset, so I can use my PV

Versions

• Chart: (1.3.0)
• Kubernetes:
  • Client: 1.11.2
  • Server: 1.11.3
• Helm:
  • Client: v2.11.0
  • Server: v2.11.0