ocfs2: send correct UUID to cleancache initialization

ocfs2: Fix cleancache initialization call to correctly pass uuid

As reported by Steven Whitehouse in https://lkml.org/lkml/2011/5/27/221
the ocfs2 volume UUID is incorrectly passed to cleancache.
As a result, shared-ephemeral tmem pools will not actually
be created; instead they will be private (unshared) which
misses out on a major benefit of tmem.

Reported-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>

fs/ocfs2/super.c

@@ -2360,7 +2360,7 @@ static int ocfs2_initialize_super(struct super_block *sb,
 		mlog_errno(status);
 		goto bail;
 	}
-	cleancache_init_shared_fs((char *)&uuid_net_key, sb);
+	cleancache_init_shared_fs((char *)&di->id2.i_super.s_uuid, sb);
 
 bail:
 	return status;