Application Service Sytests consistently fail

[anoadragon453]

Description

These three tests constantly fail since the v1.12.4 merge, when running with sytest on the dinsic-release-v1.12.x branch.

When switching the tested Synapse instance to mainline however, the tests pass without trouble.

The tests that fail all reside within the tests/60app-services/03passive.pl. If you run these tests on their own, they pass. If you run tests/60app-services/02ghost.pl and then the 03passive.pl tests in the same run, the latter will fail.

The tests spin up a fake application service which is able to listen for events and HTTP requests. The three tests expect one or more of these, and all fail as they never arrive. However, if you check Synapse's logs, it's trying to send them, but then times out after not receiving a response. So my theory is that SyTest is failing to initialize the fake application service, and probably doing so as a result of something Synapse failed to do/did differently from what mainline does.

And somehow that behaviour only surfaces if you run other tests beforehand.

I spent quite a while on this, before deciding that we need to get on with the merge, and thus have blacklisted them. However, as DINUM rely on application service functionality for shadow servers, blacklisting tests surrounding them is not a very good long-term solution.