cli/command/system:remove versionInfo.ServerOK() utility

It's defined on a non-exported type, and was only used in a template.
Replacing for a basic "nil" check, which should do the same.

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

cli/command/system/version.go

@@ -33,7 +33,7 @@ Client:{{if ne .Platform.Name ""}} {{.Platform.Name}}{{end}}
  Context:	{{.Context}}
 {{- end}}
 
-{{- if .ServerOK}}{{with .Server}}
+{{- if ne .Server nil}}{{with .Server}}
 
 Server:{{if ne .Platform.Name ""}} {{.Platform.Name}}{{end}}
  {{- range $component := .Components}}
@@ -80,12 +80,6 @@ type clientVersion struct {
 	Context           string
 }
 
-// ServerOK returns true when the client could connect to the docker server
-// and parse the information received. It returns false otherwise.
-func (v versionInfo) ServerOK() bool {
-	return v.Server != nil
-}
-
 // NewVersionCommand creates a new cobra.Command for `docker version`
 func NewVersionCommand(dockerCli command.Cli) *cobra.Command {
 	var opts versionOptions