Follow-up to #13575. Part of #13356

To improve things further we could add a limit parameter to get_current_hosts_in_room. Realistically, we don't need 4k domains to choose from because there is no way we're going to query that many before we a) probably get an answer or b) we give up.

-- Going further section in #13575

This means we can do less work in the database which means less waiting to get a list of domains to try.