[changes] Make user an admin in DEBUG mode

Summary: To simplify working on VM. I am having to manually toggle the flag in the DB. Let me know if you have any concerns.

Test Plan: Go through the auth flow on my VM (w00t!), see that I can view /admin after this

Reviewers: cramer, vishal, cf

Reviewed By: cf

Subscribers: alexallain

Maniphest Tasks: T26532

Differential Revision: https://tails.corp.dropbox.com/D81894