Fix PVC creation if SC is not specified

If SC was not configured in CLI `kreate` the PVC resource
that got created has SC set to empty string `""` which resulted
into the problem and the volume was not provisioned.
This commit fixes that by making sure that if the sc is not
configured we don't sc which would result into defalt SC being
used in the PVC.

cmd/create_pvc.go

@@ -96,7 +96,7 @@ func (o *CreatePVCOptions) Complete(f cmdutil.Factory, cmd *cobra.Command, args
 }
 
 func (o *CreatePVCOptions) createPVCObject() *corev1.PersistentVolumeClaim {
-	return &corev1.PersistentVolumeClaim{
+	pvc := &corev1.PersistentVolumeClaim{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      o.Name,
 			Namespace: o.Namespace,
@@ -107,12 +107,17 @@ func (o *CreatePVCOptions) createPVCObject() *corev1.PersistentVolumeClaim {
 					"storage": resource.MustParse(fmt.Sprintf("%sGi", o.Size)),
 				},
 			},
-			StorageClassName: &o.StorageClass,
 			AccessModes: []corev1.PersistentVolumeAccessMode{
 				corev1.ReadWriteOnce,
 			},
 		},
 	}
+
+	if o.StorageClass != "" {
+		pvc.Spec.StorageClassName = &o.StorageClass
+	}
+
+	return pvc
 }
 
 func (o *CreatePVCOptions) Run() error {