Fix 20130820.file-mailkey-populate.php for databases in strict mode

Summary:
Fixes T3803. Turns out my advice was sort of terrible. :/

In strict mode, the `INSERT INTO x (y, z)` raises an error unless `(y, z, ...)` includes //all// columns without default values.

Test Plan: Ran `storage upgrade` on a strict-mode install. Verified no inserts were performed.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3803

Differential Revision: https://secure.phabricator.com/D6894