Adjust Access Count Job to handle missing/deleted chunks

[Alexander-Dubrawski]

It can happen that chunks are going to be deleted. We need to adjust the update_chunk_data_job(https://github.com/hyrise/Cockpit/blob/dev/hyrisecockpit/database_manager/job/update_chunks_data.py) to handle this case. A first implementation to handle this problem can be found in 462a851.