popupMenu: Close menus on session mode changes

We are already closing top bar menus on session mode changes, but
as this behavior makes sense for any other menus as well - dash
context menus or the background menu for instance - just generalize
the behavior.

https://bugzilla.gnome.org/show_bug.cgi?id=787676

js/ui/panel.js

@@ -1084,8 +1084,6 @@ var Panel = new Lang.Class({
             let indicator = this.statusArea[role];
             if (!indicator)
                 continue;
-            if (indicator.menu)
-                indicator.menu.close();
             indicator.container.hide();
         }
     },

js/ui/popupMenu.js

@@ -465,6 +465,7 @@ var PopupMenuBase = new Lang.Class({
 
     _sessionUpdated: function() {
         this._setSettingsVisibility(Main.sessionMode.allowSettings);
+        this.close();
     },
 
     addAction: function(title, callback, icon) {