Fix board links in TaskDetail

Summary: Not sure if this is the correct fix, but I think it's where you intend to go?

Test Plan: Click on link in Task, get the the correct board. Click lots of links of boards and make sure everything still works.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5361

Differential Revision: https://secure.phabricator.com/D9520