main, lib: Build in standalone etcd

Standalone etcd is useful for when we don't want to use the embedded
version to make it easier to deploy somewhere or for testing.

This pulls in about the same amount of code since we already embedded
etcd previously. Since the embedded etcd feature of mgmt is not very
stable, we'll add this for now.

lib/cli.go

@@ -390,6 +390,17 @@ func CLI(cliArgs *CLIArgs) error {
 		app.Commands = append(app.Commands, commandGet)
 	}
 
+	commandEtcd := &cli.Command{
+		Name: "etcd",
+		//Aliases: []string{"e"},
+		Usage: "Run standalone etcd",
+		Action: func(*cli.Context) error {
+			// this never runs, it gets preempted in the real main()
+			return nil
+		},
+	}
+	app.Commands = append(app.Commands, commandEtcd)
+
 	app.EnableBashCompletion = true
 	return app.Run(os.Args)
 }