We actually blank "password" arguments further up in the code:

```
  let param_keys_to_hide = [                                                    
    "config:pass"; (* AD authentication password. *)                            
    "remote-password"; (* Cross-pool migration remote XS password. *)           
    "password"; (* Local XS password. *)                                        
  ] in                                                                          
  let params = List.fold_left                                                   
    (fun acc param ->                                                           
      if List.mem_assoc param acc                                               
      then List.replace_assoc param "null" acc                                  
      else acc)                                                                 
    params param_keys_to_hide in
```

This is why it's logged as "null".

It would be nice to unify this code a bit more, rather than having two separate lists of things to hide.