Use namespace label on stack volumes.

Signed-off-by: Daniel Nephin <dnephin@docker.com>
(cherry picked from commit 4013a7c6d897051bb79982230f31279ee0c9a026)
Signed-off-by: Victor Vieux <victorvieux@gmail.com>

cli/command/stack/deploy.go

@@ -347,7 +347,7 @@ func convertVolumeToMount(
 		source = stackVolume.External.Name
 	} else {
 		volumeOptions = &mount.VolumeOptions{
-			Labels: stackVolume.Labels,
+			Labels: getStackLabels(namespace.name, stackVolume.Labels),
 			NoCopy: isNoCopy(mode),
 		}