VMware: pass vm_ref to _set_machine_id

Save a method call to get the vm_ref. In spawn this value exists so
we can pass it to the method if necessary.

Change-Id: Ied43fb09fb2eec2d2c22fce17b4f98ae3f58860e

nova/tests/unit/virt/vmwareapi/test_vmops.py

@@ -871,7 +871,8 @@ class VMwareVMOpsTestCase(test.NoDBTestCase):
             mock_set_machine_id.assert_called_once_with(
                 self._session.vim.client.factory,
                 self._instance,
-                network_info)
+                network_info,
+                vm_ref='fake_vm_ref')
             if power_on:
                 mock_power_on_instance.assert_called_once_with(
                     self._session, self._instance, vm_ref='fake_vm_ref')

nova/virt/vmwareapi/vmops.py

@@ -449,7 +449,8 @@ class VMwareVMOps(object):
         # Set the machine.id parameter of the instance to inject
         # the NIC configuration inside the VM
         if CONF.flat_injected:
-            self._set_machine_id(client_factory, instance, network_info)
+            self._set_machine_id(client_factory, instance, network_info,
+                                vm_ref=vm_ref)
 
         # Set the vnc configuration of the instance, vnc port starts from 5900
         if CONF.vnc_enabled:
@@ -1244,11 +1245,13 @@ class VMwareVMOps(object):
             machine_id_str = machine_id_str + interface_str + '#'
         return machine_id_str
 
-    def _set_machine_id(self, client_factory, instance, network_info):
+    def _set_machine_id(self, client_factory, instance, network_info,
+                        vm_ref=None):
         """Set the machine id of the VM for guest tools to pick up
         and reconfigure the network interfaces.
         """
-        vm_ref = vm_util.get_vm_ref(self._session, instance)
+        if vm_ref is None:
+            vm_ref = vm_util.get_vm_ref(self._session, instance)
 
         machine_id_change_spec = vm_util.get_machine_id_change_spec(
                                  client_factory,