acme: stop using ctxhttp

The ctxhttp package used to be big and gross before net/http supported
contexts natively. Nowadays it barely does anything. Stop using it,
because it just pulls in the old context package anyway. (We can't
really clean up the ctxhttp package until Go 1.9)

Change-Id: I48b11f2f483783a32cbaa75e244301148a304c08
Run-TryBot: Brad Fitzpatrick <>
TryBot-Result: Gobot Gobot <>
Reviewed-by: Alex Vaghin <>
2 files changed