[libvirt] makes libvirt code more debian friendly

debian based libvirt does not know interfaces and some node information

lib/fog/libvirt/requests/compute/get_node_info.rb

@@ -12,10 +12,10 @@ module Fog
             node_hash[param] = client.send(param) rescue nil
           end
           node_hash[:uri] = client.uri
-          xml = client.sys_info
+          xml = client.sys_info rescue nil
           [:uuid, :manufacturer, :product, :serial].each do |attr|
             node_hash[attr] = node_attr(attr, xml)
-          end
+          end if xml
 
           node_hash[:hostname] = client.hostname
           [node_hash]

lib/fog/libvirt/requests/compute/list_interfaces.rb

@@ -5,7 +5,9 @@ module Fog
         def list_interfaces(filter = { })
           data=[]
           if filter.keys.empty?
-            (client.list_interfaces + client.list_defined_interfaces).each do |ifname|
+            active_networks = client.list_interfaces rescue []
+            defined_networks = client.list_defined_interfaces rescue []
+            (active_networks + defined_networks).each do |ifname|
               data << interface_to_attributes(client.lookup_interface_by_name(ifname))
             end
           else