don't download vsg image if it already exists

Change-Id: I9a97ac577d9ecc071ba7a4486b2ab846b18d0786
diff --git a/cord-pod/Makefile b/cord-pod/Makefile
index 78054ad..115e726 100644
--- a/cord-pod/Makefile
+++ b/cord-pod/Makefile
@@ -184,7 +184,7 @@
 	#bash -c "source ../setup/admin-openrc.sh; glance image-show ceilometer-service-trusty-server-multi-nic || wget http://www.vicci.org/cord/ceilometer-service-trusty-server-multi-nic.compressed.qcow2 -P ./images"
 
 images/vsg-1.0.img: images
-	wget http://www.vicci.org/cord/vsg-1.0.img -P ./images
+	[ -s images/vsg-1.0.img ] || wget http://www.vicci.org/cord/vsg-1.0.img -P ./images
 
 images:
 	mkdir -p ./images