nfs41: create NFSv3 DS connection if specified

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Tom Haynes <Thomas.Haynes@primarydata.com>

fs/nfs/nfs4super.c

@@ -346,6 +346,9 @@ out:
 
 static void __exit exit_nfs_v4(void)
 {
+	/* Not called in the _init(), conditionally loaded */
+	nfs4_pnfs_v3_ds_connect_unload();
+
 	unregister_nfs_version(&nfs_v4);
 	nfs4_unregister_sysctl();
 	nfs_idmap_quit();