cmd/coordinated: send http request logs to stdout instead of stderr
cmd/coordinated: send http request logs to stdout instead of stderr

This allows them to better mesh with various external systems
that provide log visualization, such as Google Cloud Stackdriver,
which interprets stdout/stderr as levels in the UI. HTTP request
logs should not be considered "errors".

This is a fix building on top of the work in:
https://github.com/diffeo/go-coordinate/pull/22

diffeo/go-coordinate