ASGARD-1193 - Stop collecting unlimited host names

Collecting host names in ServerController.hostNames has never turned out to be useful, and it's recently been found to be dangerous when there is a lot of traffic. Delete it from ServerController and from TrackingFilters and anywhere else it shows up.
Merge pull request #355 from joesondow/ASGARD-1193-don't-collect-host-names

ASGARD-1193 - Stop collecting unlimited host names