shellDBus: Fix reloadExtension

We need to recreate and reimport the extension here, not just reimport
the same exact code.

https://bugzilla.gnome.org/show_bug.cgi?id=682578

js/ui/shellDBus.js

@@ -318,8 +318,11 @@ const GnomeShellExtensions = new Lang.Class({
     },
 
     ReloadExtension: function(uuid) {
-        ExtensionSystem.unloadExtension(uuid);
-        ExtensionSystem.loadExtension(uuid);
+        let extension = ExtensionUtils.extensions[uuid];
+        if (!extension)
+            return;
+
+        ExtensionSystem.reloadExtension(extension);
     },
 
     CheckForUpdates: function() {