Fix CORS in devhub test receipts (bug 1104371)

This also fixes the CORS decorator which was
previously broken for OPTIONS requests.

@mstriemer r?
:+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1::+1: