Add configtest subcommand. skip un-ssh-able servers.

commands/prepare.go

@@ -153,11 +153,7 @@ func (p *PrepareCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interface{
 	logger := util.NewCustomLogger(c.ServerInfo{})
 
 	logger.Info("Detecting OS... ")
-	err = scan.InitServers(logger)
-	if err != nil {
-		logger.Errorf("Failed to init servers. err: %s", err)
-		return subcommands.ExitFailure
-	}
+	scan.InitServers(logger)
 
 	logger.Info("Installing...")
 	if errs := scan.Prepare(); 0 < len(errs) {