Change Caddyfile path not set and Swarm not available logs to Debug

[jonatasbaldin]

Hi there!

First, thanks a lot for this project, it is very useful!

When running caddy-docker-proxy without a Caddyfile or Swarm mode enabled, the log messages below are emitted every polling interval (default for 30s).

caddy_1  | {"level":"info","ts":1645116020.518531,"logger":"docker-proxy","msg":"Skipping swarm services because swarm is not available"}
caddy_1  | {"level":"info","ts":1645116050.5464995,"logger":"docker-proxy","msg":"Skipping default Caddyfile because no path is set"}
caddy_1  | {"level":"info","ts":1645116050.54652,"logger":"docker-proxy","msg":"Skipping swarm config caddyfiles because swarm is not available"}
caddy_1  | {"level":"info","ts":1645116050.5493286,"logger":"docker-proxy","msg":"Skipping swarm services because swarm is not available"}
caddy_1  | {"level":"info","ts":1645116080.5410242,"logger":"docker-proxy","msg":"Skipping default Caddyfile because no path is set"}
...

This can be too verbose when running without a Caddyfile or Swarm. This PR changes these two log messages from Info to Debug.

I believe it offers a better user experience by avoiding emitting unnecessary logs.