Check the network_info obj type before invoke wait function

When instance schedule to host and it isn't first time schedule,
the instance may already allocated network. And then the code
will return an NetworkInfo object, not an NetworkInfoAsyncWrapper.
The checking code only assume it is NetworkInfoAsyncWrapper object.

Change-Id: I987902fc47e509e4fd08f762d66b16c09eaf5008
Partial-Bug: #1326207

nova/network/model.py

@@ -380,6 +380,14 @@ class NetworkInfo(list):
     def json(self):
         return jsonutils.dumps(self)
 
+    def wait(self, do_raise=True):
+        """A no-op method.
+
+        This is useful to avoid type checking when NetworkInfo might be
+        subclassed with NetworkInfoAsyncWrapper.
+        """
+        pass
+
 
 class NetworkInfoAsyncWrapper(NetworkInfo):
     """Wrapper around NetworkInfo that allows retrieving NetworkInfo

nova/tests/compute/test_compute_mgr.py

@@ -1820,6 +1820,30 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
                     mock.call(self.context, self.instance,
                         self.requested_networks, self.security_groups))
 
+    def test_build_resources_with_network_info_obj_on_spawn_failure(self):
+        self.mox.StubOutWithMock(self.compute, '_cleanup_build_resources')
+        self.mox.StubOutWithMock(self.compute, '_build_networks_for_instance')
+        self.compute._build_networks_for_instance(self.context, self.instance,
+                self.requested_networks, self.security_groups).AndReturn(
+                        network_model.NetworkInfo())
+        self._build_resources_instance_update()
+        self.compute._cleanup_build_resources(self.context, self.instance,
+                self.block_device_mapping)
+        self.mox.ReplayAll()
+
+        test_exception = test.TestingException()
+
+        def fake_spawn():
+            raise test_exception
+
+        try:
+            with self.compute._build_resources(self.context, self.instance,
+                    self.requested_networks, self.security_groups,
+                    self.image, self.block_device_mapping):
+                fake_spawn()
+        except Exception as e:
+            self.assertEqual(test_exception, e)
+
     def test_build_resources_cleans_up_and_reraises_on_spawn_failure(self):
         self.mox.StubOutWithMock(self.compute, '_cleanup_build_resources')
         self.mox.StubOutWithMock(self.compute, '_build_networks_for_instance')