make sort controls only show up if sorting will work

Summary: T2326 tells the tale. this is the fix.

Test Plan: verified that queries that shouldn't be sortable weren't. also had a phlog in there a bit to sanity check things faster

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2326

Differential Revision: https://secure.phabricator.com/D4816