Description of problem:
using oc volume set ...  --claim-class=<...> does not set the `storageClassName:`
in the created pvc which in turn makes this volume not eligible for snapshots as the VolumeSnaphotClass has a dependency to the original storage class 


Version-Release number of selected component (if applicable):
ocp 4.6.24  with OCS 4.6 or OCS 4.7 (rc)
ocp 4.7.7 with OCS 4.7 (rc)

How reproducible:


Steps to Reproduce:
1. create OCP 4.6.24 or OCP 4.7.7 cluster
2. deploy OCS 4.6 or 4.7 on top of it
3. create  pods (e.g. like shown here https://red-hat-storage.github.io/ocs-training/training/ocs4/ocs.html#_create_a_new_ocp_application_deployment_using_cephfs_volume )

4. especially set volume with 
`oc set volume deploy/file-uploader --add --name=my-shared-storage \
-t pvc --claim-mode=ReadWriteMany --claim-size=1Gi \
--claim-name=my-shared-storage --claim-class=ocs-storagecluster-cephfs \
--mount-path=/opt/app-root/src/uploaded \
-n my-shared-storage`

5. Try to get snapshot via ui --> Snapshot Class is empty and cannot be chosen 

Actual results:

it is not possible to create a snapshot from a volume created with 

oc set volume deploy/file-uploader --add --name=my-shared-storage \
-t pvc --claim-mode=ReadWriteMany --claim-size=1Gi \
--claim-name=my-shared-storage --claim-class=ocs-storagecluster-cephfs \
--mount-path=/opt/app-root/src/uploaded \
-n my-shared-storage

looking at the created pvc with oc edit, I see 

~~~
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  annotations:
    pv.kubernetes.io/bind-completed: "yes"
    pv.kubernetes.io/bound-by-controller: "yes"
    volume.beta.kubernetes.io/storage-class: ocs-storagecluster-cephfs
    volume.beta.kubernetes.io/storage-provisioner: openshift-storage.cephfs.csi.ceph.com
  creationTimestamp: "2021-04-27T14:01:00Z"
  finalizers:
  - kubernetes.io/pvc-protection
  name: my-shared-storage
  namespace: my-shared-storage
  resourceVersion: "49103"
  selfLink: /api/v1/namespaces/my-shared-storage/persistentvolumeclaims/my-shared-storage
  uid: a4a7a5b7-38f3-4009-8a40-9bbfd4a5ec19
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
  volumeMode: Filesystem
  volumeName: pvc-a4a7a5b7-38f3-4009-8a40-9bbfd4a5ec19
status:
  accessModes:
  - ReadWriteMany
  capacity:
    storage: 1Gi
  phase: Bound

~~~

so no storageClassName added 


Expected results:

storageClassName added to the created pvc as specified by oc volume set ...  --claim-class=<...> 



Additional info:

If I do edit the created pvc and add the storageClassName to it:

~~~
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  annotations:
    pv.kubernetes.io/bind-completed: "yes"
    pv.kubernetes.io/bound-by-controller: "yes"
    volume.beta.kubernetes.io/storage-class: ocs-storagecluster-cephfs
    volume.beta.kubernetes.io/storage-provisioner: openshift-storage.cephfs.csi.ceph.com
  creationTimestamp: "2021-04-27T15:01:00Z"
  finalizers:
  - kubernetes.io/pvc-protection
  name: my-shared-storage
  namespace: my-shared-storage
  resourceVersion: "49312"
  selfLink: /api/v1/namespaces/my-shared-storage/persistentvolumeclaims/my-shared-storage
  uid: a4a7a5b7-38f3-4009-8a40-9bbfd4a5ec19
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
  storageClassName: ocs-storagecluster-cephfs  <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
  volumeMode: Filesystem
  volumeName: pvc-a4a7a5b7-38f3-4009-8a40-9bbfd4a5ec19
status:
  accessModes:
  - ReadWriteMany
  capacity:
    storage: 1Gi
  phase: Bound

~~~


I see in the UI a Snapshot Class prefilled and can create a snapshot