Subcommand OnUsageError should be passed to app

Not all of the Command components were being passed to the created App
in the startApp function.

command.go

@@ -291,6 +291,7 @@ func (c Command) startApp(ctx *Context) error {
 	} else {
 		app.Action = helpSubcommand.Action
 	}
+	app.OnUsageError = c.OnUsageError
 
 	for index, cc := range app.Commands {
 		app.Commands[index].commandNamePath = []string{c.Name, cc.Name}