Fix refresh profile picture functionality

Summary:
turns out both github and Phabricator fall back to if the user already has a login session when accessing the pertinent profile picture data. Facebook on the other hand is a stingy bastard about have an actual access token. Ergo, in production (once I could test Facebook) this button failed.

The patch sets the access token properly such that the provider can use it properly when retrieving the profile image.

Test Plan: re-did my meta-Phabricator test and it still passed. setup my phabricator dev instance for Facebook OAuth (created a test app and everything... :/ ) and it worked end to end.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Maniphest Tasks: T870

Differential Revision: https://secure.phabricator.com/D1986