Allow public countdowns to be viewed by logged out users
Summary: Fixes T5093. Ref T4830.
Test Plan:
- As a logged out user, viewed a public countdown detail page.
- (Tried to view a nonpublic one, got asked to login.)
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T4830, T5093
Differential Revision: https://secure.phabricator.com/D9162