Updating tower topology for the tutorial.

Change-Id: I5310d0fad33fe2dfbd4135fd350696c4d5a36458
diff --git a/tools/test/topos/tower.json b/tools/test/topos/tower.json
new file mode 100644
index 0000000..7f7d426
--- /dev/null
+++ b/tools/test/topos/tower.json
@@ -0,0 +1,13 @@
+{
+  "devices": {
+    "of:0000000000000001": { "basic": { "name": "Spine-1" }},
+    "of:0000000000000002": { "basic": { "name": "Spine-2" }},
+    "of:0000000000000003": { "basic": { "name": "Leaf-1" }},
+    "of:0000000000000004": { "basic": { "name": "Leaf-2" }},
+    "of:0000000000000005": { "basic": { "name": "Leaf-3" }},
+    "of:0000000000000006": { "basic": { "name": "Leaf-4" }}
+  },
+
+  "hosts": {
+  }
+}