Fix bug occurring when shutting down instance with no active appserver.

Created by: smarnach

This bug was encountered by @bdero when shutting down unused beta test instances.

The bug occurs when an instance without any active appserver is shut down. This case triggered a special code path, which was not covered by the tests. I added a test to cover it.

I also removed the if clause that triggered that special code path, since it's not needed anymore in the current version. (It was needed at some point.) I leave the test in anyway.

For testing, create an instance, spawn an appserver, and shut the instance down without activating the appserver.