AI now handles EMP-stun like other creatures do in their life.dm file

Previously AI would be stunned indefinitely after being hit with an EMP-blast. This would prevent emergency shutters from being operated.
The stun status is now adjusted down in the Life()-proc like is done in the base living.dm, which the AI living.dm does not ..() call.
Merge pull request #5379 from PsiOmegaDelta/AIStun

AI now handles the sunned status like other creatures do in their life.dm file