cli/command/stack: minor cleanups: use Println, rename vars

- use Println to print newline instead of custom format
- use dockerCLI with Go's standard camelCase casing.
- suppress some errors to make my IDE and linters happier

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/stack/loader/loader.go

@@ -40,13 +40,13 @@ func LoadComposefile(dockerCli command.Cli, opts options.Deploy) (*composetypes.
 
 	unsupportedProperties := loader.GetUnsupportedProperties(dicts...)
 	if len(unsupportedProperties) > 0 {
-		fmt.Fprintf(dockerCli.Err(), "Ignoring unsupported options: %s\n\n",
+		_, _ = fmt.Fprintf(dockerCli.Err(), "Ignoring unsupported options: %s\n\n",
 			strings.Join(unsupportedProperties, ", "))
 	}
 
 	deprecatedProperties := loader.GetDeprecatedProperties(dicts...)
 	if len(deprecatedProperties) > 0 {
-		fmt.Fprintf(dockerCli.Err(), "Ignoring deprecated options:\n\n%s\n\n",
+		_, _ = fmt.Fprintf(dockerCli.Err(), "Ignoring deprecated options:\n\n%s\n\n",
 			propertyWarnings(deprecatedProperties))
 	}
 	return config, nil