Pass whole PVC to provisioner plugin

Gluster provisioner is interested in pvc.Namespace and I don't want to add
at as a new field in VolumeOptions - it would contain almost whole PVC.

Let's pass direct reference to PVC instead and let the provisioner to pick
information it is interested in.

pkg/volume/rbd/rbd_util.go

@@ -314,7 +314,8 @@ func (util *RBDUtil) DetachDisk(c rbdUnmounter, mntPath string) error {
 }
 
 func (util *RBDUtil) CreateImage(p *rbdVolumeProvisioner) (r *api.RBDVolumeSource, size int, err error) {
-	volSizeBytes := p.options.Capacity.Value()
+	capacity := p.options.PVC.Spec.Resources.Requests[api.ResourceName(api.ResourceStorage)]
+	volSizeBytes := capacity.Value()
 	// convert to MB that rbd defaults on
 	sz := int(volume.RoundUpSize(volSizeBytes, 1024*1024))
 	volSz := fmt.Sprintf("%d", sz)