Summary:
Currently the algorithm for calculating frames will not always have an correct value for the endframe making some natively driven animations stuck almost at the end. This PR ensures the animation ends at `1`.
**Test plan**
Tested with the code in `NativeAnimationsExample.js`.
Closes https://github.com/facebook/react-native/pull/8489
Differential Revision: D3502973
fbshipit-source-id: b9b114d3982341571ac6ff315620d3d2292d9266