Make status icons centered in PHUI object list view

Summary: Fixes T8789. This makes status icons centered in the PHUI object list view.

Test Plan: Looked at it.

Reviewers: #blessed_reviewers, chad

Reviewed By: #blessed_reviewers, chad

Subscribers: epriestley

Maniphest Tasks: T8789

Differential Revision: https://secure.phabricator.com/D13592