Horse Doesn't Move/Buck While Taming

Taming horses works, but a wild horse stands still after mounting despite making running sound effects. However, it will still buck the player off.

What I expected to happen was:
I expected the wild horse to run around as it did in 1.8.9 and previous versions.

What actually happened was:
It stood still. Once tame, hearts rose and it started walking around like normal.

Steps to Reproduce:
1. Find a wild horse or spawn one in creative.
2. Mount it.
3. Notice that it stands still, but still has running sound effects.