We have a lot of forged users that have bad fullnames due to
historical versions of our fullname computations; this function will
clean those up.
Also, we have a bunch of users with emails like foo|mit.edu@mit.edu
that were the result of a mirroring bug that we want to get rid of
from autocomplete -- putting them in a useless realm name will do.
(imported from commit 6e305093653ca9d327e9e28491636e99d16cfe1d)
