Try to get to the bottom of the sporradic test failures in testColumnExtendedPolicies()

Summary:
This test has been failing occasionally in a way that does not reproduce, and only when no one is looking at it.

Try to add some extra assertions to maybe get more information.

Test Plan: arc unit

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D16137