Improve the layout when listing non-vlan clients via 'info network'. The
result looks like this:

(qemu) info network
Devices not on any VLAN:
  orphan: net=10.0.2.0, restricted=n
  virtio-net-pci.0: model=virtio-net-pci,macaddr=52:54:00:12:34:56
   \ network2: fd=5
  e1000.0: model=e1000,macaddr=52:54:00:12:34:57
   \ network1: net=10.0.2.0, restricted=n
  rtl8139.0: model=rtl8139,macaddr=52:54:00:12:34:58

ie. peers are grouped, orphans are listed as before.

CC: Markus Armbruster <armbru@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>