need to close the multiprocessing pool (#28)

Co-authored-by: dustinlo <[email protected]>

purge.py

@@ -86,6 +86,7 @@ def purge_products(query, component, operation, delete_from_obj_store=True):
             p.map(delete_from_object_store, results)  # deleting objects from storage (s3, etc.)
         else:
             logger.info("skip purging datasets from object store. delete_from_object_store=False")
+        p.close()
 
         dataset_purge_stats = {}
         deleted_docs_count = 0