I don’t know why libvirt is trying to use the 16509 port - that should be commented out by default in /etc/libvirt/libvirtd.conf on test6. I imagine you have no problems creating a test VM from test6 manually with virt-install, as root?
virsh list --all
grep oneadmin /etc/libvirt/qemu.conf # opennebula modifies this file
yum -y install wget virt-install virt-viewer
wget https://download.cirros-cloud.net/0.4.0/cirros-0.4.0-i386-disk.img -P /tmp
chown oneadmin:oneadmin /tmp/cirros-0.4.0-i386-disk.img
virt-install --os-variant=virtio26 --name=cirros --ram=64 --vcpus=1 --disk /tmp/cirros-0.4.0-i386-disk.img,format=qcow2 --import --nonetworks
In another terminal, with $DISPLAY available:
virt-viewer cirros # just check if it starts fine
virsh destroy cirros
virsh undefine cirros