On @username mentions in remarkup, show the "busy" dot color

Summary:
Ref T11809. I missed this when adding a "Busy" status.

Also the other dot is orange? Just make them all orange for consistency.

Test Plan: Viewed @username of busy users (orange), away users (red).

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11809

Differential Revision: https://secure.phabricator.com/D16819