Harmonize logging fields (and values) across code base.

Problem to solve

Currently some fields that report the same information in log messages have different identifiers, for example, in the tape daemon code, for exception messages we have: exceptionMSG, exceptionMsg, exceptionMessage, exceptionMessageValue. And we also have a table in Grafana which looks for exception_message which does not exist in CTA's code base.

Proposal

Review all logging, standardize, document and fix the inconsistencies.