Fix an issue with multiple "open" statuses and the "View All" button on Projects

Summary: See IRC. We construct this a little bit wrong if there are multiple "open" statuses. Use a more modern construction.

Test Plan: Hit `?statuses=wontfix,invalid`, etc. Clicked "view all" from projects.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D8854