Don't validate Conduit hosts

Summary:
(See rPd1d3bf4e / rPf371c7b3.) Just get rid of this logic, I don't think there's any value to it.

IIRC, this was added a long time ago to deal with some issues that users had configuring things, but I think modern Phabricator covers all this stuff and I haven't seen any confusion from users for a year or more.

(Generally, I want to generally make Conduit easier to use, and this makes it more difficult.)

Test Plan: `grep`

Reviewers: joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9703