Fix CDROM upgrader.

CDROM does not have most of the utilities installed that the main
image does.  This is to preserve the number of photons in the
universe by burning fewer of them to keep our ISO smaller.

So work around not having mkfifo(1), logger(1) and a few other
utils by piping output to a file in that failure case.

(cherry picked from commit 399c46e38e308db66708823dc3fa061f1dd0b1d4)