Add --oauth2, move update_backend on its own rule
Add --oauth2, move update_backend on its own rule

Fix update_indexed and vacuum_indexes to specify --application.

Review: https://codereview.appspot.com/13364044/

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra