Praser.py: payload_config selection behaviour in the case of expired flight doc about habitat HOT 1 OPEN

Going for old but approved flight docs might make sense before looking for latest payload docs (which we'd still do as a final fallback if no flight docs have the payload).

The problem here is that if you want to test a new payload config document, your old flight document will always take precedence -- so you could never test a new payload on the same callsign without making (and having approved) a flight for it.

On balance it seems like helping users whose flight docs have expired is less useful than preventing testing. Can anyone think of a way around that?

from habitat.