[MC-30685] Minecraft - Mob Speed Effect Bug

Put the summary of the bug you're having here

What I expected to happen was...:
The creeper with the speed effect would move faster.

What actually happened was...:
It moved the same speed as the creeper without the speed effect.

Steps to Reproduce:

/summon Creeper ~ ~ ~ {Fuse:1,ActiveEffects:[Id:1,Amplifier:5,Duration:9999}]}