This patch add vnc_display_reload_certs() to support
update x509 certificates.

Signed-off-by: Zihao Chang <changzihao1@huawei.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210316075845.1476-3-changzihao1@huawei.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>