fix support for VMware vCenter Driver

Change-Id: Iedd26dbb89731f49718604eb09eb84b3e0b648c0
diff --git a/stackrc b/stackrc
index c55e8dc..f99eab1 100644
--- a/stackrc
+++ b/stackrc
@@ -199,6 +199,8 @@
                 IMAGE_URLS=${IMAGE_URLS:-"http://download.cirros-cloud.net/0.3.1/cirros-0.3.1-x86_64-uec.tar.gz"};;
         esac
         ;;
+    vsphere)
+        IMAGE_URLS="";;
     *) # otherwise, use the uec style image (with kernel, ramdisk, disk)
         DEFAULT_IMAGE_NAME=${DEFAULT_IMAGE_NAME:-cirros-0.3.1-x86_64-uec}
         IMAGE_URLS=${IMAGE_URLS:-"http://download.cirros-cloud.net/0.3.1/cirros-0.3.1-x86_64-uec.tar.gz"};;