Stop ignoring errors when the test fixture fails to delete data files

The standalone test fixture attempts to delete data files before starting a node. We ignore errors when deleting data files, so we don't know if the deletion was successful. An example of when a deletion could fail is on Windows when another process is keeping the file open. When we fail to delete data files, tests can fail because they expect to start up with clean data files. We should add logging to understand when we fail to delete data files.