style fix menusystem

src/opnsense/mvc/app/views/layout_partials/base_menu_system.volt

 <aside id="navigation" class="page-side col-xs-12 col-sm-2 hidden-xs">
     <div class="row">
         <nav class="page-side-nav" role="navigation">
-            <div class="list-group" id="mainmenu">
+            <div id="mainmenu" class="panel">
                 {% for topMenuItem in menuSystem %}
+                <div class="panel list-group">
                     <a href="#{{ topMenuItem.Id }}" class="list-group-item {% if topMenuItem.Selected %}  active-menu-title {% endif  %}" data-toggle="collapse" data-parent="#mainmenu"><span class="{{ topMenuItem.CssClass }} __iconspacer"></span>{{ topMenuItem.VisibleName }} </a>
                     <div class="collapse  {% if topMenuItem.Selected %} active-menu in {% endif  %}" id="{{ topMenuItem.Id }}">
                         {% for subMenuItem in topMenuItem.Children %}
@@ -11,6 +12,7 @@
                             {% endif %}
                         {% endfor %}
                     </div>
+                </div>
                 {% endfor %}
             </div>
         </nav>