libvirt: Introduce Guest.get_config method

There are some places in libvirt driver code which have to get and parse
domain xml manually. This patch adds get_config method to Guest object,
dedicated to be used there instead.

Change-Id: I9a28570ebe00f9973aaa9ed2c7f2d5254fd1216e

nova/tests/unit/virt/libvirt/test_guest.py

@@ -359,6 +359,14 @@ class GuestTestCase(test.NoDBTestCase):
         self.guest.set_user_password("foo", "123")
         self.domain.setUserPassword.assert_called_once_with("foo", "123", 0)
 
+    def test_get_config(self):
+        xml = "<domain type='kvm'><name>fake</name></domain>"
+        self.domain.XMLDesc.return_value = xml
+        result = self.guest.get_config()
+        self.assertIsInstance(result, vconfig.LibvirtConfigGuest)
+        self.assertEqual('kvm', result.virt_type)
+        self.assertEqual('fake', result.name)
+
     def test_get_devices(self):
         xml = """
 <domain type='qemu'>

nova/virt/libvirt/guest.py

@@ -308,6 +308,15 @@ class Guest(object):
         LOG.debug("attach device xml: %s", device_xml)
         self._domain.attachDeviceFlags(device_xml, flags=flags)
 
+    def get_config(self):
+        """Returns the config instance for a guest
+
+        :returns: LibvirtConfigGuest instance
+        """
+        config = vconfig.LibvirtConfigGuest()
+        config.parse_str(self._domain.XMLDesc(0))
+        return config
+
     def get_disk(self, device):
         """Returns the disk mounted at device