sqlite default filename is not Windows compatible

[untr0py]

File model_search/metadata/ml_metadata_db.py, lines 102-103 are:

        self._connection_config.sqlite.filename_uri = (
            "/tmp/filedb-%d" % random.randint(0, 1000000))

/tmp/... is of course not a valid path for Windows.
Can you update this path such that it chooses a valid path when running on Windows?