CERT_PKEY_SIGN isn't meaningful since, without strict mode, we always fall back
to SHA-1 anyway. So the digest is never NULL when CERT_PKEY_SIGN is computed.
The entire valid_flags is now back to it's pre-1.0.2 check of seeing if the
certificate and key are configured.
This finally removes the sensitivity between valid_flags and selecting the
digest, so we can defer choosing the digest all we like.
Change-Id: I9f9952498f512d7f0cc799497f7c5b52145a48af
Reviewed-on: https://boringssl-review.googlesource.com/2288
Reviewed-by: Adam Langley <agl@google.com>
033e5f47d1