How to reproduce:
1. Open attached "TimelineTest" project and "Test" scene
2. Select the "Director" GameObject and open Timeline window, observe that this Timeline has an Activation Track that activates the Sphere GameObject
3. Stop preview mode by pressing “Preview” button in the Timeline editor, observe Sphere being deactivated
4. Start playback in the Timeline editor and add an animation key to the animation track by double-clicking the animation curve
5. Stop playback and exit preview mode

Expected result - Sphere has its Active state reverted (is deactivated)
Actual result - Sphere does not have its state reverted (is active)

Regression introduced in - 2017.1.0b8
Reproducible with - 2017.3.0a7, 2017.2.0b11, 2017.1.1p1, 2017.1.0b8
Not reproducible with - 2017.1.0b7