Each test environment in internal/ircserver named its shared in-memory
database after the test. A repeat run of a test in the same process
could open the database that an earlier run's server was still
holding, and start on that run's users. The database now gets a random
name, and a new test checks that two environments open at once do not
share one.
The database close and the server stop are now registered as soon as
each is opened, so a setup that fails part-way still closes its
database.
Model: opus-5-5
