Yes sir - here we are ... you are right.
With xen, you DO NOT need the "system" in the URL.
The following works for xen - but not for qemu:
[root@xen04 ~]$ virsh -c
xen+tls://xen04.domainname.com list
Id Name State
This is a little bit inconsequent/confusing (-:
But, if it's known, it's easy...
regards
Danny