Remove the need of defining __get_entries thru __get_attribute__

Due to a wrong parameter passed to the dunder __setattr__ method
which was '__entries' instead of '_NodeConfig__entries' we ran
into the RecursionError, because __getattr__ was calling itself
since '__entries' attribute cannot be found.

For more information read the `Note` here:
https://docs.python.org/3/library/functions.html#getattr

Fixes pylint error:
- package/test_tools/__private/node_config.py:129:15: C2801: Unnecessarily calls dunder method __getattribute__. Access attribute directly or use getattr built-in function. (unnecessary-dunder-call)