Show providers in login order, not alphabetical order

Summary: Ref T1536. Mostly, this puts "username/password" (which is probably a common selection) first on the list.

Test Plan: {F47010}

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T1536

Differential Revision: https://secure.phabricator.com/D6254