MFC r266444:
  We have two functions from where a geom orphan method could be called:
  g_orphan_register and g_resize_provider_event. Both are called from the
  event queue. Also we have GEOM_DEV class, which does deferred destroy
  for its consumers via g_dev_destroy (also called from the event queue).
  So it is possible, that for some consumers an orphan method will be
  called twice. This triggers panic in g_dev_orphan.
  Check that consumer isn't already orphaned before call orphan method.