Disable stack growth when accessed by AIO daemons.

Commit message for r321173 incorrectly stated that the change disables
automatic stack growth from the AIO daemons contexts, with explanation
that this is currently prevents applying wrong resource limits. Fix
this by actually disabling the growth.

Noted by: alc
Reviewed by: alc, jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week