docker info: don't print "registry" (IndexServerAddress)

The IndexServerAddress field was  as part of the initial Windows implementation
of the engine. For legal reasons, Microsoft Windows (and thus Docker images
based on Windows) were not allowed to be distributed through non-Microsoft
infrastructure. As a temporary solution, a dedicated "registry-win-tp3.docker.io"
registry was created to serve Windows images.

Currently, this field always shows "https://index.docker.io/v1/", which is
confusing, because that address is not used for the registry (only for
authentication and "v1" search).

    docker info
    ...
    Registry: https://index.docker.io/v1/

Starting with b4ca1c7368daeead400fcc1b8f2d61951a0d9d1e, this field is also
no longer used during authentication, and a3d56e7d067b38b98548a864436880eef526f971
removed the (deprecated) ElectAuthServer() which was previously used to
query it.

Given that there's currently no practical use for this information, and
it only adds "noise" (and confusion), this patch removes it from the default
output.

For now, the field is (still) available for those that want to use it;

    docker info --format '{{.IndexServerAddress}}'
    https://index.docker.io/v1/

But it won't be printed by default.

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

cli/command/system/info.go

@@ -324,7 +324,6 @@ func prettyPrintServerInfo(dockerCli command.Cli, info types.Info) []error {
 		if len(u) > 0 {
 			fmt.Fprintln(dockerCli.Out(), " Username:", u)
 		}
-		fmt.Fprintln(dockerCli.Out(), " Registry:", info.IndexServerAddress)
 	}
 
 	if len(info.Labels) > 0 {

cli/command/system/testdata/docker-info-badsec.golden

@@ -41,7 +41,6 @@ Server:
   Goroutines: 135
   System Time: 2017-08-24T17:44:34.077811894Z
   EventsListeners: 0
- Registry: https://index.docker.io/v1/
  Labels:
   provider=digitalocean
  Experimental: false

cli/command/system/testdata/docker-info-no-swarm.golden

@@ -46,7 +46,6 @@ Server:
   Goroutines: 135
   System Time: 2017-08-24T17:44:34.077811894Z
   EventsListeners: 0
- Registry: https://index.docker.io/v1/
  Labels:
   provider=digitalocean
  Experimental: false

cli/command/system/testdata/docker-info-plugins.golden

@@ -51,7 +51,6 @@ Server:
   Goroutines: 135
   System Time: 2017-08-24T17:44:34.077811894Z
   EventsListeners: 0
- Registry: https://index.docker.io/v1/
  Labels:
   provider=digitalocean
  Experimental: false

cli/command/system/testdata/docker-info-with-labels-empty.golden

@@ -45,7 +45,6 @@ Server:
   Goroutines: 135
   System Time: 2017-08-24T17:44:34.077811894Z
   EventsListeners: 0
- Registry: https://index.docker.io/v1/
  Experimental: false
  Insecure Registries:
   127.0.0.0/8

cli/command/system/testdata/docker-info-with-labels-nil.golden

@@ -45,7 +45,6 @@ Server:
   Goroutines: 135
   System Time: 2017-08-24T17:44:34.077811894Z
   EventsListeners: 0
- Registry: https://index.docker.io/v1/
  Experimental: false
  Insecure Registries:
   127.0.0.0/8

cli/command/system/testdata/docker-info-with-swarm.golden

@@ -67,7 +67,6 @@ Server:
   Goroutines: 135
   System Time: 2017-08-24T17:44:34.077811894Z
   EventsListeners: 0
- Registry: https://index.docker.io/v1/
  Labels:
   provider=digitalocean
  Experimental: false

docs/reference/commandline/info.md

@@ -102,7 +102,6 @@ Server:
  Docker Root Dir: /var/lib/docker
  Debug Mode: false
  Username: gordontheturtle
- Registry: https://index.docker.io/v1/
  Experimental: false
  Insecure Registries:
   myinsecurehost:5000
@@ -164,7 +163,6 @@ Server:
  ID: 2880d38d-464e-4d01-91bd-c76f33ba3981
  Docker Root Dir: C:\ProgramData\docker
  Debug Mode: false
- Registry: https://index.docker.io/v1/
  Experimental: true
  Insecure Registries:
   myregistry:5000

man/src/system/info.md

@@ -82,7 +82,6 @@ Server:
  Docker Root Dir: /var/lib/docker
  Debug Mode: false
  Username: gordontheturtle
- Registry: https://index.docker.io/v1/
  Experimental: false
  Insecure Registries:
   myinsecurehost:5000