Fix integration test execution on Dron

Apparently the Nextcloud server ignores tests that have `Integration` in their
fully-qualified class name, hence the backup codes integration tests were removed.
This moves them up one directory (out of `Integration`) to fix that.
Real unit tests remain in the `Unit` directory.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>