ONOS-4359: continued work on theming UI (app control buttons).

Change-Id: I87c510caee499a2ecaa51241785e300cb06c1f61
(cherry picked from commit a705605)
diff --git a/web/gui/src/main/webapp/app/fw/mast/mast.css b/web/gui/src/main/webapp/app/fw/mast/mast.css
index 57353b0..ef982bb 100644
--- a/web/gui/src/main/webapp/app/fw/mast/mast.css
+++ b/web/gui/src/main/webapp/app/fw/mast/mast.css
@@ -23,6 +23,10 @@
     padding: 0;
 }
 
+#mast a:hover {
+    text-decoration: none;
+}
+
 html[data-platform='iPad'] #mast {
     padding-top: 16px;
 }