drive-menu: ignore shadowed mounts

Shadow mounts are created by the GVolume infrastructure to wrap
daemon mounts managed by volume monitors, and are an implementation
detail that should not be exposed to the user.

extensions/drive-menu/extension.js

@@ -133,6 +133,8 @@ const DriveMenu = new Lang.Class({
     _isMountInteresting: function(mount) {
         if (!mount.can_eject() && !mount.can_unmount())
             return false;
+        if (mount.is_shadowed())
+            return false;
 
         let volume = mount.get_volume();