--cleanup doesn't clean up the last_seen entries for --not-after locations

[mricon]

E.g. if someone logs in from 192.168.1.1 and the admin sets --not-after on that location, if the user logs in from the same IP address after the --not-after date, the last-seen match will continue to match.

Solution: During cleanup, run an additional check on last-seen locations and delete those that don't have a matching location in the locations db.