Reproduction Steps:
1. Open "BugReproductionProject" project
2. Select "legL" object (child of "Body")
3. In animation window delete second key
4. Change object rotation z axis value to -35 (write in and press Return)
5. Preview animation
6. Notice that it goes the long way around
Note: There is User's video showing the exact steps and the bug itself.

Expected: It makes differences if the value written in is negative (it goes opposite direction).

Reproduced in versions: Unity 5.3.5f1, 5.3.5p5
Not reproducible in versions: Unity 5.3.4f1, 5.4.0b22