virsh: Add interface name completion to iface-mac command

Signed-off-by: Lin Ma <lma@suse.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

tools/virsh-interface.c

@@ -441,6 +441,7 @@ static const vshCmdOptDef opts_interface_mac[] = {
     {.name = "interface",
      .type = VSH_OT_DATA,
      .flags = VSH_OFLAG_REQ,
+     .completer = virshInterfaceNameCompleter,
      .help = N_("interface name")
     },
     {.name = NULL}