[a-c-r] Handle case of canceling container that is already cancelled.
(Total: 0.00 h)
When the user hits control-C on a running instance of a-c-r, the shutdown process cancels the container request by updating the request to set priority to 0. If there is a race condition and container request was already final (but a-c-r didn't notice yet), this will raise an exception trying to update a finalized container. This exception should be caught and suppressed (if the request is already finalized it doesn't need to be cancelled).