Backed the change out on changeset:   8298:cfa7d43a3658.

back_sqlite and back_mysql both have the following comment in setid:

    def setid(self, classname, setid):
        """ Set the id counter: used during import of database

        We add one to make it behave like the sequences in postgres.
        """

so my change broke testing in CI (I must have skipped testing or testmon didn't
run the right tests).

We lose one id on import. Hopefully people aren't exporting/importing and using
up a lot of ids.