Default logging backend and doc guidance

[rocketraman]

Logging is configured to use syslog. This means docker logs does not work. And docker service logs <servicename> just hangs without producing any output.

Please provide some guidance in the documentation about how to manage logging within Azure and swarm mode. According to moby/moby#24812 this should generally be working, but perhaps not with the syslog configured default. The default setup should probably allow docker service logs to work correctly, and then people can modify their logging setup as desired from there.

[FrenchBen]

This is actually documented within the Docker docs, please see:
https://docs.docker.com/docker-for-azure/faqs/#/where-are-my-container-logs

[rocketraman]

Somehow I missed that, thanks.