Differential - stop showing the shield for "move away" operations

Summary: The shield is just confusing. In one case it doesn't work, and in the other case it just shows you a copy of the file you can see just below except in red. Fixes T4599, T1211. Note T1211 proposed not showing the "move away" file at all but I think removing the shield fixes the source of confusion. The code here is a bit if / else if / else if... heavy but this is logically sound.

Test Plan: made a diff where i moved a file then edited it in the new location. viewed diff, saw confusing shield, dropped caches, applied patch, viewed diff and saw no shield. made a diff where I moved a file and didn't edit in new location and saw similar shield disappearness.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T1211, T4599

Differential Revision: https://secure.phabricator.com/D10865