RM7980

A commit back in may introduced filtering on "do_not_use" when selecting
IP addresses from the database. Unfortunately, this had the unintended
side-effect of applying a cartesian product to the result set, crushing
neutron DB servers in the process. This patch refactors the join to be
more sensible, as well as an inner join for safety.
Merge pull request #170 from Cerberus98/master

RM7980