dirstate-v2: actually fix the dirstate-v2 upgrade race It looks like the previous fix for the dirstate-v2 upgrade race didn't work. The problem is that it only recovers in case the size of the v1 `dirstate` file is smaller than the `v2` one, whereas in real life it's always larger. This commit changes the test to be more realistic, which reveals the crash, and changes the code to fix the crash.