Use the password stored in the secret driver under
the uuid specified by the vnc_tls_x509_secret_uuid
option in qemu.conf.

https://bugzilla.redhat.com/show_bug.cgi?id=1602418Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>