Fix fedup version logging

Commit 65f8f5f added fedup.version and wrote it into the log, but the
imports were a little screwy. Make sure we actually import the right
stuff.
Fix ValueError with --addrepo/--repo REPOID (#1045090)

We need to be sure that the argument to --addrepo is actually of the
form "REPOID=[@]URL", or we end up with a ValueError when we try to
split it into two parts later on. So let's check that early.

Also, the --repo argument was deprecated and hidden, and it's now
causing confusion with --instrepo, so drop it.