Adjust object_compat wrapper order

There's a comment on object_compat usage:
if the method being decorated has more than one decorator, then
put this one first. Otherwise the various exception handling
decorators do not function correctly.

Even though it says to remove object_compat function after I release
it's still there , so this patch adjust the order of the usage.

Change-Id: I4eb14cd595e8e0f9e0b7e0aacd5bb1299c0c9c00

nova/compute/manager.py

@@ -4420,12 +4420,12 @@ class ComputeManager(manager.Manager):
         else:
             return '\n'.join(log.split('\n')[-int(length):])
 
+    @object_compat
     @messaging.expected_exceptions(exception.ConsoleTypeInvalid,
                                    exception.InstanceNotReady,
                                    exception.InstanceNotFound,
                                    exception.ConsoleTypeUnavailable,
                                    NotImplementedError)
-    @object_compat
     @wrap_exception()
     @wrap_instance_fault
     def get_vnc_console(self, context, console_type, instance):