Description of problem:
If the storage size is specified and storageClassName is not set. the clusterlogging operator generate the pvc resource file using storageClassName: "".   that cause the pvc couldn't be bind as there isn't storageClassName "".

If we want to use default storage class, Remove the storageclass from the PVC resource file.  if we want to use storageClassName as mandatory. We need to update the document.



Version-Release number of selected component (if applicable):
clusterlogging operator v4.x

How reproducible:
Always

Steps to Reproduce:
1. provide logging CLO Resource without storageclass options.
apiVersion: "logging.openshift.io/v1alpha1"
kind: "ClusterLogging"
metadata:
  name: "nostorageclassname"
spec:
  managementState: "Managed"
  logStore:
    type: "elasticsearch"
    elasticsearch:
      nodeCount: 3
      resources:
        limits:
          memory: 2Gi
        requests:
          cpu: 200m
          memory: 2Gi
      storage:
        size: "20G"
      redundancyPolicy: "SingleRedundancy"
  visualization:
    type: "kibana"
    kibana:
      replicas: 1
  curation:
    type: "curator"
    curator:
      schedule: "*/10 * * * *"
  collection:
    logs:
      type: "fluentd"
      fluentd: {}

2. Check the pvc status
 oc get pvc 
 oc edit pvc

Actual results:
The pvc could't be binding as the storageclass name is "".

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  creationTimestamp: 2019-03-18T02:37:36Z
  finalizers:
  - kubernetes.io/pvc-protection
  name: elasticsearch-elasticsearch-clientdatamaster-0-3
  namespace: openshift-logging
  resourceVersion: "27499"
  selfLink: /api/v1/namespaces/openshift-logging/persistentvolumeclaims/elasticsearch-elasticsearch-clientdatamaster-0-3
  uid: ca5f2068-4926-11e9-b285-0a3cd40e33ca
spec:
  accessModes:
  - ReadWriteOnce
  dataSource: null
  resources:
    requests:
      storage: 20G
  storageClassName: ""
status:
  phase: Pending


Expected results:
A) Remove the storageclass option from pvc.  so the pvc can use the default storageclass.
B) indicate storageclass is a mandatory variable