minecraft 14w28b mobs are non stop spawning in spawners

Put the summary of the bug you're having here

What I expected to happen was waithing for mobs to spawn in the spawner...:
Describe what you thought should happen here

What actually happened was the spawner was non stop spawning...:
Describe what happened here

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. go to a spawner ...
3. and the spawner is non stop spawning mobs...