Fixing a bug with self._value_func, which was returning the func_state, rather than just the value of the loss, when value_func_has_aux=False and value_func_has_state=True.

Fixing a bug with self._value_func, which was returning the func_state, rather than just the value of the loss, when value_func_has_aux=False and value_func_has_state=True. #881