Put bango back as default provider on stage/prod

Regression from
https://github.com/mozilla/webpay/commit/ea1e8a5e46c75a180f5c301f5a0dcf44098ef204#diff-dd105a0d42e09344f9547443a623c831L520
Merge pull request #509 from kumar303/pay-settings

Put bango back as default provider on stage/prod