Complete Aggregation on route stop broken

When attempting to stop a route that has exchanges in flight they should be processed and aggregated before shutdown but instead they all throw RejectedExecutionException and are not processed.
In camel 2.9.2 they are processed and aggregated as expected before the route is shutdown. But the same code does not work in any further versions of camel.
Attached is a sample test that displays the above error. Simply changing the version of camel will cause the test to pass.