Code review comment for ~paulgear/ntp-charm/+git/ntp-charm:chrony-support

Looks good.

I do strongly believe that the ntp_implementation config option should be dropped, as its only use case is to create broken or unsupported deployments. The function in ntp_implementation.py can keep its auto mode, since it is really external/shared code rather than part of the charm, but the charm should always call it with 'auto'. Not only does a foot-gun option not encode best practice like the charm should, but it will also cause problems in a few years when we drop Xenial support and the NTP code along with it.