Contain fallout from overheating feed queries on user profile pages

Summary: Fixes T13349. If the user profile page feed query overheats, it currently takes the whole page with it. Contain the blast to a smaller radius.

Test Plan: {F6633322}

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13349

Differential Revision: https://secure.phabricator.com/D20678