Before SERVER-107304 we needed a special flag agg::Pipeline::_disposeInDestructor and the method agg::Pipeline::dismissDisposal() to prevent agg::Pipeline to auto-dispose in destructor while being 'detached' from the valid operation context instance.

However, after SERVER-107304 agg::Pipeline::dispose() prevents itself from being called repeatedly, so technically we can remove agg::Pipeline::_disposeInDestructor and agg::Pipeline::dismissDisposal() for general simplification.