Cover redirects to files in more cases

Summary: Ref T5894. We have a couple more similar cases. Make them all do a decision-based redirect for now.

Test Plan: Did "View Raw File" and such, and also made sure thumbnails still work.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5894

Differential Revision: https://secure.phabricator.com/D10301