Dnat Wrangler code cleanup

https://github.com/dice-cyfronet/atmosphere/issues/59
Unused method argument - `appliance`. If it's necessary, use `_` or `_appliance` as an argument name to indicate that it won't be used. You can also write as `can_afford_flavors?(*)` if you want the method to accept any arguments but don't care about them.<br>Unused method argument - `flavors`. If it's necessary, use `_` or `_flavors` as an argument name to indicate that it won't be used. You can also write as `can_afford_flavors?(*)` if you want the method to accept any arguments but don't care about them.