MINOR: ocsp: Do not see ocsp loading failures as fatal anymore
Until now, if the call to 'ssl_sock_load_ocsp' raised an error, because
of a missing issuer certificate for instance, we would send a fatal
error code and the init would fail.
With this patch we only consider this as a non-critical error and we
will send a warning instead. In such a case the OCSP response will not
be loaded and stapling or auto update features will not work for the
certificate.