fix: don't duplicate logger fields

[truszkowski]

Now, we have duplicated fields in logs:

{... "msg":"scaling down ASG and killing worker", ... , "aws_request_id": "...", "aws_request_id": "...", ... "worker_id": "...", "instance_id": "...", "worker_id": "...", "instance_id": "...", ... }

We should reuse the logger, and just pass with new fields to the new logger variable.