ONOS-3182 added swap functionality

Change-Id: Idc521a330c5bb3c0e0a47f66a90dfa95855e610f
diff --git a/web/gui/src/main/webapp/app/view/topo/topoToolbar.js b/web/gui/src/main/webapp/app/view/topo/topoToolbar.js
index 804e2a3..fbcdaf6 100644
--- a/web/gui/src/main/webapp/app/view/topo/topoToolbar.js
+++ b/web/gui/src/main/webapp/app/view/topo/topoToolbar.js
@@ -167,7 +167,7 @@
 
         // generate radio button set for overlays; start with 'none'
         var rset = [{
-                gid: 'topo',
+                gid: 'unknown',
                 tooltip: 'No Overlay',
                 cb: function () {
                     tov.tbSelection(null, switchOverlayActions);