Some mild refactoring of the docker info command;
- Use `fmt.Fprinln()` instead of `fmt.Fprintf()` where possible
- Rename `fprintfIfNotEmpty()` to `fprintlnNonEmpty()`, and removed
return variables, because they were not used. `fprintlnNonEmpty()`
now uses fmt.Fprintln()` instead of `fmt.Fprintf()`, because
formatting was not used.
- Use `fprintlnNonEmpty()` to get rid of some `if` statements
- Extract printing Swarm-related information to a `printSwarmInfo()` function
- Change `Http Proxy` and `Https Proxy` to `HTTP Proxy` / `HTTPS Proxy`
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
6f1b510843