This makes Ed25519 certificates work for CreateCRL(). This previously
failed (panic: crypto: requested hash function #0 is unavailable) because
the hash could not be skipped, but Ed25519 uses no hash.

A similar fix has been applied in a few other places when Ed25519 was added
when Ed25519 certificates were originally introduced, but was missed
here.

Change-Id: I16fcfcd53ba3bb8f773e5de972b8fedde1f6350e

Change-Id: I16fcfcd53ba3bb8f773e5de972b8fedde1f6350e
GitHub-Last-Rev: bf7f1458f850d01605c619c3f53f86649477dd4d
GitHub-Pull-Request: golang/go#35241
Reviewed-on: https://go-review.googlesource.com/c/go/+/204046
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>