acme: add v3 implementation to RevokeAuthorization

Let's Encrypt apparently implements authorization revocation as specified
in the v3 of the spec:
https://tools.ietf.org/html/draft-ietf-acme-acme-03#section-6.4.2.

See the relevant boulder source code here:
https://github.com/letsencrypt/boulder/blob/be01ca17d334f73823a9c69afbcf99d777482547/wfe/wfe.go#L1177-L1213

This change makes RevokeAuthorization compatible with both v2 and v3
versions of the spec, as well as Let's Encrypt staging/production
actual implementation.

Change-Id: I7e860944005a55b156a45d96e1b8eb41126ce6bb
Reviewed-on: https://go-review.googlesource.com/31990
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed