When renaming $dest_dir to $old_dir, don't say we're renaming
$new_dir to $old_dir on errors.

--- a/atomic-rsync
+++ b/atomic-rsync
@@ -48,7 +48,7 @@ if (system($RSYNC_PROG, "--link-dest=$dest_dir", @ARGV)) {
     exit $?;
 }
 
-rename($dest_dir, $old_dir) or die "Unable to rename $new_dir to $old_dir: $!";
+rename($dest_dir, $old_dir) or die "Unable to rename $dest_dir to $old_dir: $!"
 rename($new_dir, $dest_dir) or die "Unable to rename $new_dir to $dest_dir: $!"
 
 exit;