triggered a payment forwarding.
Final onions may trigger a payment forwarding, through the callback
returned by maybe_fulfill_htlc. In that case, we should not fail the
HTLC later; doing so might result in fund loss.
Remove test_simple_payment_with_hold_invoice_timing_out: once we
have accepted to forward a payment HTLC with a hold invoice, we
do not want to time it out, for the same reason.
141cd524bc