Always include the current user as a selectable policy

Summary: Ref T4136. After Passphrase, user policies work correctly in this dropdown. Providing this option improves consistency and makes it easier to create, e.g., a private repository (where "no one" does not include the viewer, because they don't own the resulting object).

Test Plan: Set an object's policy to my user policy.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4136

Differential Revision: https://secure.phabricator.com/D7858