Race between ctxt shutdown, after suite listeners and reporters

I understand that this issue duplicates or even causes #103.

Both the spring ctxt shutdown as well as the after suite notifications are being run in parallel in two different JVM shutdown hooks. Now interacting with ctxt beans while shutting down the ctxt at the same time is an error-prone race.

What seems to me as a potential solution to this problem is introducing an `@Order`ed race-free shutdown sequence moving the `AfterSuiteShutdownHook` to be a `ApplicationListener` participating in the spring ctxt shutdown.

@christophd?