When reading certificate fail, we should stop the communication between the requester and responder

[Zhiqiang520]

Test at the commit 2c4ada8

The line 248, 264, and 278 just handle the case when res = TRUE, I think we should also handle the other case when res = FALSE.
When read certificate fail, we should stop the communication between the requester and responder, maybe just like the following three lines sample code(bold text).
free(m_spdm_context);
m_spdm_context = NULL;
return NULL;

spdm-emu/spdm_emu/spdm_requester_emu/spdm_requester.c

Lines 244 to 292 in eea369c

	res = read_responder_public_certificate_chain(m_use_hash_algo,
	m_use_asym_algo,
	&data, &data_size,
	NULL, NULL);
	if (res) {
	zero_mem(&parameter, sizeof(parameter));
	parameter.location = SPDM_DATA_LOCATION_LOCAL;
	spdm_set_data(spdm_context,
	SPDM_DATA_PEER_PUBLIC_CERT_CHAIN,
	&parameter, data, data_size);
	// Do not free it.
	}
	} else {
	res = read_responder_root_public_certificate(m_use_hash_algo,
	m_use_asym_algo,
	&data, &data_size,
	&hash, &hash_size);
	x509_get_cert_from_cert_chain((uint8 *)data + sizeof(spdm_cert_chain_t) + hash_size,
	data_size - sizeof(spdm_cert_chain_t) - hash_size, 0,
	&root_cert, &root_cert_size);
	if (res) {
	zero_mem(&parameter, sizeof(parameter));
	parameter.location = SPDM_DATA_LOCATION_LOCAL;
	spdm_set_data(spdm_context,
	SPDM_DATA_PEER_PUBLIC_ROOT_CERT,
	&parameter, root_cert, root_cert_size);
	// Do not free it.
	}
	}
	res = read_requester_public_certificate_chain(m_use_hash_algo,
	m_use_req_asym_algo,
	&data, &data_size, NULL,
	NULL);
	if (res) {
	zero_mem(&parameter, sizeof(parameter));
	parameter.location = SPDM_DATA_LOCATION_LOCAL;
	data8 = m_use_slot_count;
	spdm_set_data(spdm_context, SPDM_DATA_LOCAL_SLOT_COUNT,
	&parameter, &data8, sizeof(data8));
	for (index = 0; index < m_use_slot_count; index++) {
	parameter.additional_data[0] = index;
	spdm_set_data(spdm_context,
	SPDM_DATA_LOCAL_PUBLIC_CERT_CHAIN,
	&parameter, data, data_size);
	}
	// do not free it
	}