Improve utilization of "AuthTemporaryToken" table keys in LFS authentication queries

Summary:
See PHI1123. The key on this table is <resource, type, code> but we currently query for only <type, code>. This can't use the key.

Constrain the query to the resource we expect (the repository) so it can use the key.

Test Plan: Pushed files using LFS. See PHI1123 for more, likely.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20261