[NFS]: NFS super blocks in different VEs are different

Teach nfs_compare_super to this.

Signed-off-by: Denis V. Lunev <den@openvz.org>
-------
--- ./fs/nfs/super.c.nfs1	2008-05-27 16:33:43.000000000 +0400
+++ ./fs/nfs/super.c	2008-05-27 16:34:50.000000000 +0400
@@ -1020,6 +1020,9 @@ static int nfs_compare_super(struct supe
 		return 0;
 	if (old->addr.sin_port != server->addr.sin_port)
 		return 0;
+	if (!ve_accessible_strict(old->client->cl_xprt->owner_env,
+				  get_exec_env()))
+		return 0;
 	return !nfs_compare_fh(&old->fh, &server->fh);
 }