Fix passing no user into user_has_host() not properly looking up user
Only validate hosts for the linking bot, not all

This fixes the previous code causing the first user to have the matching
host to be returned, thus causing a non-match on the user handle and
then denying the link. This change now allows multiple users/bots
to have the same hostname, but requires that the linking bot
matches its own hosts
Merge branch 'protect-telnet-user-match' into next

* protect-telnet-user-match:
  Only validate hosts for the linking bot, not all
  Fix passing no user into user_has_host() not properly looking up user