Floating buttons can be changed only after `NavigationViewController` is presented

[azarovalex]

Consider this code:

let navigationViewController = NavigationViewController(for: response, routeIndex: 0, routeOptions: routeOptions, navigationOptions: navigationOptions)
navigationViewController.floatingButtons = []

This code won't work because ornamentsController inside of NavigationViewController will be created only in viewDidLoad. We can trigger view load in floatingButtons getter to fix the problem.