gst/gstbin.c: Don't forget about the fact that some element went ASYNC even after a resync. This makes us post the AS...

Original commit message from CVS:
* gst/gstbin.c: (gst_bin_change_state_func),
(bin_handle_async_done), (gst_bin_handle_message_func):
Don't forget about the fact that some element went ASYNC even after a
resync. This makes us post the ASYNC_DONE message correctly.
Fixes #462558.