With built-in verification on, a server certificate verifier returning
true made Mbed TLS accept a certificate its own check had rejected,
such as a self-signed one, while OpenSSL and wolfSSL still failed with
SSLServerVerification. On a client, keep the flags of Mbed TLS's own
verification, so the verifier is an additional check as on the other
backends. With verification off, the verifier is still the only check.
A server still clears them: there all three backends let an accepting
callback admit a client certificate.
yhirose
906a7bf04e
