Do not make the ingest folder

A folder that Bindery made hid a missing volume mount. The books went
to a folder inside the container, and CWA never saw them. A missing
folder is now an error in the log at the start, and each upload fails
with a message that names the mount.

tests/conftest.py

@@ -7,6 +7,7 @@ from pathlib import Path
 _tmp = Path(tempfile.mkdtemp(prefix="bindery-tests-"))
 for name, sub in [("CONFIG_DIR", "config"), ("INGEST_DIR", "ingest"), ("TMP_DIR", "tmp")]:
     os.environ[name] = str(_tmp / sub)
+(_tmp / "ingest").mkdir()  # Bindery does not make the ingest folder
 os.environ["BINDERY_START_THREADS"] = "false"
 os.environ["UPDATE_INTERVAL_HOURS"] = "0"
 for name in (