Description of problem
----------------------

When deploying an OCS StorageCluster with Ceph FS disabled and Ceph RBD enabled, the VolumeSnapshotClass for Ceph RBD is not created.

Steps to Reproduce
------------------

Create an OCS StorageCluster with Ceph FS disabled and Ceph RBD enabled:

> ---
> kind: StorageCluster
> apiVersion: ocs.openshift.io/v1
> metadata:
>   name: ocs-storagecluster
>   namespace: openshift-storage
> spec:
>   managedResources:
>     cephBlockPools:
>       reconcileStrategy: manage
>     cephFilesystems:
>       reconcileStrategy: ignore
> [...] 

Actual results
--------------

Ceph File System is not deployed as expected.
Ceph RBD is deployed but its VolumeSnapshotClass is not created.

Expected results
----------------

VolumeSnapshotClass for Ceph RBD (ocs-storagecluster-rbdplugin-snapclass) should be created.

Additional info
---------------

Looking at the code the issue seems due to a copy/paste mistake:

=> https://github.com/openshift/ocs-operator/blob/master/controllers/storagecluster/volumesnapshotterclasses.go

> func newCephFilesystemSnapshotClassConfiguration(instance *ocsv1.StorageCluster) SnapshotClassConfiguration {
> 	return SnapshotClassConfiguration{
> 		snapshotClass:     newVolumeSnapshotClass(instance, cephfsSnapshotter),
> 		reconcileStrategy: ReconcileStrategy(instance.Spec.ManagedResources.CephFilesystems.ReconcileStrategy),
> 		disable:           instance.Spec.ManagedResources.CephFilesystems.DisableSnapshotClass,
> 	}
> }
> 
> func newCephBlockPoolSnapshotClassConfiguration(instance *ocsv1.StorageCluster) SnapshotClassConfiguration {
> 	return SnapshotClassConfiguration{
> 		snapshotClass:     newVolumeSnapshotClass(instance, rbdSnapshotter),
> 		reconcileStrategy: ReconcileStrategy(instance.Spec.ManagedResources.CephFilesystems.ReconcileStrategy),
> 		disable:           instance.Spec.ManagedResources.CephFilesystems.DisableSnapshotClass,
> 	}
> }

The function newCephBlockPoolSnapshotClassConfiguration uses Ceph FS configuration (instance.Spec.ManagedResources.CephFilesystems) instead of Ceph RDB configuration (instance.Spec.ManagedResources.CephBlockPools).