Show default settings in mysql sample config

[danielnelson]

The sample config now shows the default values. I added new defaults for the perf events since the existing defaults were not usable and the plugin required them to be set.

  # perf_events_statements_digest_text_limit = 120
  # perf_events_statements_limit = 250
  # perf_events_statements_time_limit = 86400

closes #6444

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[glinton]

Wouldn't this (and others) negatively affect those generating and using the config file?

[danielnelson]

Can you give an example of what might happen?

[glinton]

This changes the default/generated config file, so if anyone is relying on these values, telegraf will no longer do what they are expecting. In this case, the process list would no longer be gathered unless manual action is taken on their part, whereas before no action was required.

[danielnelson]

I see, a newly generated config would be different from a generated config in the previous version. The reason I think this is okay is that previously generated configs will continue to work as before. The default values aren't changing (with the exception of the values in the first comment) they were documented incorrectly.