Bug#819869: nvidia-legacy-check: lock during install

[殷啟聰]

This is not the problem of debconf. After dpkg started unpacking the
package it froze, and some mimutes later the terminal gave "NMI watch
dog soft lockup" errors.

I added "acpi=off" to GRUB boot options and I succeeded in installing
this package.

Before turning off ACPI, runing "lspci" always stopped forever, and I
noticed the preinstall scripts has "lspci" usage, so maybe that was
the problem.