GUI -- Do not display IconLibDefs SVG element.

Change-Id: I883b512a86a509afdb14352ef340d9bce9a09349
diff --git a/web/gui/src/main/webapp/app/fw/svg/icon.css b/web/gui/src/main/webapp/app/fw/svg/icon.css
index bd431c7..a05493d 100644
--- a/web/gui/src/main/webapp/app/fw/svg/icon.css
+++ b/web/gui/src/main/webapp/app/fw/svg/icon.css
@@ -18,6 +18,10 @@
  ONOS GUI -- Icon Service -- CSS file
  */
 
+svg#IconLibDefs {
+  display: none;
+}
+
 svg.embeddedIcon .icon .glyph {
  stroke: none;
  fill: white;