Adds datasetUUID for referencing flocker datasets

* flocker datasets should be attached using an unique identifier. This
  is not the case for the name metadata used by datasetName
* allow only one of datasetUUID / datasetName specified

pkg/api/zz_generated.deepcopy.go

@@ -1178,6 +1178,7 @@ func DeepCopy_api_FlockerVolumeSource(in interface{}, out interface{}, c *conver
 		in := in.(*FlockerVolumeSource)
 		out := out.(*FlockerVolumeSource)
 		out.DatasetName = in.DatasetName
+		out.DatasetUUID = in.DatasetUUID
 		return nil
 	}
 }