test: Fix tests to reduce chance of "database is locked" error.

[terriko]

I'm getting more of these errors in CI lately:

sqlite3.OperationalError: database is locked

While these crop up somewhat randomly when we try to run a lot of tests in parallel, it would be really nice to have two things:

1. Make sure -u never or equivalent is set in all tests unless the update code is what's being tested.
2. Any tests that do need to call update code should be moved into the long tests "synchronous" group so that we don't try to run them all at once. I thought most of them were in there or the network-may-fail group but we may have missed one or more.

I think those two test fixes are both pretty doable by a beginner. I'd also like to handle a back off and retry when that error is thrown, but I'll put that in a separate issue since it may be harder.

[dhruvi003]

Hi! I'm new to open source and would like to work on this issue. Could you please assign it to me?

[terriko]

@dhruvi003 thanks for your interest, but I think we've got several other people working on this at the moment.