Add the check for deleting snapshot while creating volume

If the snapshot is currently being deleted, the deletionTimestamp is
set, and provisioner should not try to create the volume in this case.

Author: jingxu97

pkg/controller/controller.go

@@ -541,6 +541,9 @@ func (p *csiProvisioner) getVolumeContentSource(options controller.VolumeOptions
 		return nil, fmt.Errorf("snapshot %s is not Ready", options.PVC.Spec.DataSource.Name)
 	}
 
+	if snapshotObj.ObjectMeta.DeletionTimestamp != nil {
+		return nil, fmt.Errorf("snapshot %s is currently being deleted", options.PVC.Spec.DataSource.Name)
+	}
 	glog.V(5).Infof("VolumeSnapshot %+v", snapshotObj)
 
 	snapContentObj, err := p.snapshotClient.VolumesnapshotV1alpha1().VolumeSnapshotContents().Get(snapshotObj.Spec.SnapshotContentName, metav1.GetOptions{})