cli/command/system: prettyPrintServerInfo: simplify username

Starting with b4ca1c7, docker login
no longer depends on info.IndexServerAddress to determine the default
registry.

The prettyPrintServerInfo() still depended on this information, which
could potentially show the wrong information.

This patch changes it to also depend on the same information as docker login
now does.

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

Author: thaJeztah

cli/command/system/info.go

@@ -19,6 +19,7 @@ import (
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/swarm"
 	"github.com/docker/docker/api/types/versions"
+	"github.com/docker/docker/registry"
 	"github.com/docker/go-units"
 	"github.com/spf13/cobra"
 )
@@ -319,12 +320,8 @@ func prettyPrintServerInfo(dockerCli command.Cli, info types.Info) []error {
 	fprintlnNonEmpty(dockerCli.Out(), " HTTPS Proxy:", info.HTTPSProxy)
 	fprintlnNonEmpty(dockerCli.Out(), " No Proxy:", info.NoProxy)
 
-	if info.IndexServerAddress != "" {
-		u := dockerCli.ConfigFile().AuthConfigs[info.IndexServerAddress].Username
-		if len(u) > 0 {
-			fmt.Fprintln(dockerCli.Out(), " Username:", u)
-		}
-	}
+	u := dockerCli.ConfigFile().AuthConfigs[registry.IndexServer].Username
+	fprintlnNonEmpty(dockerCli.Out(), " Username:", u)
 
 	if len(info.Labels) > 0 {
 		fmt.Fprintln(dockerCli.Out(), " Labels:")