lvm2: Only install results of most recently started vgs_task_func

Fixes storaged-project#966

modules/lvm2/udiskslinuxmodulelvm2.c

@@ -59,6 +59,8 @@ struct _UDisksLinuxModuleLVM2 {
 
   gint delayed_update_id;
   gboolean coldplug_done;
+
+  gint vgs_task_id;
 };
 
 typedef struct _UDisksLinuxModuleLVM2Class UDisksLinuxModuleLVM2Class;
@@ -221,6 +223,12 @@ lvm_update_vgs (GObject      *source_obj,
   gpointer key, value;
   const gchar *vg_name;
 
+  if (GPOINTER_TO_INT (user_data) != module->vgs_task_id)
+    {
+      vgs_pvs_data_free (data);
+      return;
+    }
+
   if (! data)
     {
       if (error)
@@ -303,11 +311,13 @@ lvm_update (UDisksLinuxModuleLVM2 *module)
 {
   GTask *task;
 
+  module->vgs_task_id++;
+
   /* the callback (lvm_update_vgs) is called in the default main loop (context) */
   task = g_task_new (module,
                      NULL /* cancellable */,
                      lvm_update_vgs,
-                     NULL /* callback_data */);
+                     GINT_TO_POINTER (module->vgs_task_id));
 
   /* holds a reference to 'task' until it is finished */
   g_task_run_in_thread (task, (GTaskThreadFunc) vgs_task_func);