JCLOUDS-788 Added new method to support the passing of a custom node nam...

...e when generating the chef bootstrap node script
Instead of providing a new function with most of the code duplicated, I'd simply add the `nodeName` parameter, annotated as `@Nullable`, to the existing one, and remove the `implements Function<String, Statement>` from its declaration. That it not used, as we are injecting directly the `GroupToBootScript` type, so you should be able to remove it without issues.