TimeStretchCurve doesn't work in Animation Montage

Using a TimeStretchCurve in an Animation Montage doesn't cause it to slow down or speed up when keys are added to the curve. 

Link to API: [Link Removed]

This was reported and tested in 4.20.3 (CL-4369336). This was reproduced in 4.19.2 (CL-4033788) and Main 4.22 (CL-4435744)

1. Open the UE4 Editor and create a Third Person Blueprint project
2. In the Content Browser create an Animation Montage and open it
3. Add an animation to the Montage
4. Add a Variable Curve
5. Set and move keys on the Curve

Result: Nothing happens

Expected: The Montage speeds up or slows down as described in its API.