Hostdb tests

This PR ended up going a lot different direction that I was expecting. I wrote a few tests, decided that the way we were doing things was bad, then decided that I wasn't sure of a better way to do things. So after a lot of contemplation, I decided that it's premature to be trying to make a great hostdb.

I did wrote a scanning function which will move hosts from inactive to active, something that thus far didn't exist. I also added 2 api calls, one which will tell you the list of active hosts, and one which will tell you the list of inactive hosts.