Reduce default logging volume of Event Broker

Currently all events to do with check operation are logged, so every time a check operation runs the following is logged:

1) Starting
2) Did anything change?
3) Yes/No
4) Stopping

Four logs (in a lot more words) per run, even at 30 seconds polling intervals (default) this can be a lot.

Consider updating the usage of logging levels to relegate this behaviour to Verbose, while more important (exceptional) events (e.g. 3) Yes) remain normal.