DatabaseUpdater: Stop inserting junk into 'updatelog' every time the updater runs

DatabaseUpdater: Stop inserting junk into 'updatelog' every time the updater runs

Nothing ever looks at these rows, and if you have update.php in a Cron
job or a Git hook or something, they can accumulate in huge numbers.

Also remove a test which verified that the rows get inserted.

If you reached this place while trying to find out what the weird
"updatelist-1.28.0-14628929450" rows in your database are, rest
assured they are useless. If they're causing disk space problems,
you can delete them:

  DELETE FROM updatelog WHERE ul_key LIKE 'updatelist-%';

Change-Id: If94f243810e82ea3724cbd47b301bb96ba9a49d9