Fix a Phortune billing issue where subscription autopay could charge disabled cards

Summary:
See support email. There's nothing tricky here, we were just missing a check. The different parts of this got built at different times so I think this was simply overlooked.

Also add a redundant check just to future-proof this and be on the safe side.

Test Plan: Used bin/phortune invoice to charge a pact subscription. After deleting the card, the charge failed with an appropriate error.

Reviewers: amckinley

Differential Revision: https://secure.phabricator.com/D19020