tests: teach `killdaemons` on Windows to use an exit code provided by a caller Right now, there are several tests that use `signal.SIGKILL`, which isn't a thing on Windows. The `killdaemons` script approximates this by forcibly terminating the process. There's a minor difference in that `signal.SIGKILL` results in the test capturing an exit code of 137, and the `killdaemons` victim doesn't record a code (as though it exited with 0). Since the exit code line couldn't be conditionalized the last time I checked, let's just allow the caller to simulate the same exit code, and avoid conditionalizing the tests.