Upgrade to unstable make it cannot mount root fs

[YunQiang Su <wzssyqa@gmail.com>]

I installed an Debian GNU/kFreeBSD (Stable),
 then updated it to unstable, I can not boot it now.

When process the kernel boot, it ask me to input root fs like:

ufs:/dev/ad0s9

After typed, it still ask me to input.

if set by kFreeBSD.mountfrom, it will kernel panic.

The newly installed instance has the same problem.

-- 
YunQiang Su