Menu items for both controllers are visible in toolbar during transaction

I have an app with two simple `Controller`s and it performs an animated transaction (with a `HorizontalChangeHandler()`) between them. Each controller has `setHasOptionsMenu(true)` and has its own set of toolbar icons inflated in `onCreateOptionsMenu()`.

The problem I am seeing is that right after switching animation starts both sets of icons are visible in toolbar, i.e. new ones are added right away. After animation finishes only second set of items is left visible, so the end state is correct.

But it's a bit weird to see them jump like that and seeing both sets at once. Is this an expected behavior (for which there's some traditional solution)? Or is this some bug?

I am using a freshly baked Conductor version: `2.0.1`

Reproduce the transaction with two Controllers, each using setHasOptionsMenu(true), separate toolbar items, and HorizontalChangeHandler(). Observe when each controller's onCreateOptionsMenu() output is added during the animation, then compare the toolbar state before, during, and after the transition. Done means the behavior is characterized and the issue's reported intermediate toolbar state is covered by an appropriate regression test or clearly explained.

Written by the indexing model from the issue text.