[2187437] The storageclass option is not respected in add volume modal for "Use existing volume"

+++ This bug was initially created as a clone of Bug #2186763 +++

Description of problem:
Try to add a bootable volume, select "use existing volume" and select a different storageclass from this volume, after the volume is created, the storageclass is not the one which is selected in the modal.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. open "add volume" modal
2. select "use existing volume"
3. select a pvc, eg which has storage class "hostpath-csi-basic"
4. select the storage class option "ocs-storagecluster-ceph-rbd"
5. create the volume

Actual results:
The storageClass of the created volume is "hostpath-csi-basic"

Expected results:
The SC of the created volume is "ocs-storagecluster-ceph-rbd" as it's the selected option.

Additional info: