trash: Sync trash dir items when files change

The gvfsd-trash will sync trash-items in filesystem directories to trash-dir and trash-root during it's running. When a file is deleted to the recycle bin on the mounted device, the trash_dir_changed() function will be called back to synchronize the trash-item to the trash-root. However, the trash-item is not synchronized to the trash-dir, which will cause that when the device is unmounted, all the trash-items belonging to the device cannot be deleted from the trash-root through trash-dir. The solution is to sync trash-item to trash-dir when files are trashed.