XrdHttp - Wrong handling of SSL_Shutdown() in XrdHttpProtocol::Cleanup()

[ccaffy]

We see a lot of messages of SSL_shutdown failed in the logs.

This is due to the following code in XrdHttpProtocol::Cleanup():

if (SSL_shutdown(ssl) != 1) {
      TRACE(ALL, " SSL_shutdown failed");
      ERR_print_errors(sslbio_err);
    }

The documentation of SSL_shutdown says that it is only when the return code of SSL_shutdown() is <0 that there is a fatal error: https://www.openssl.org/docs/man1.0.2/man3/SSL_shutdown.html

I'll therefore change this behaviour.

[ccaffy]

Done and merged.