Fix flaky restart-related tests

[bfops]

We have several tests that are flaky semi-regularly in our smoketests CI. Let's investigate whether the tests are flaky or if SpacetimeDB is flaky, and fix accordingly.

• test_restart_disconnects
• smoketests.tests.zz_docker.DockerRestartModule.test_restart_module
• smoketests.tests.zz_docker.DockerRestartSql.test_restart_module

[kim]

I think it might be caused by the tests resuming too early after a restart, when the server hasn't fully come up again. It's unclear though why this is the case.

[kim]

I see why it's not working, assigning myself.

[bfops]

Fixed in #2977