Run a --oneshot loop twice

This was necessary since the first loop only ever collects file
statistics so that the second run can be sure about "readiness".

src/documents/management/commands/document_consumer.py

@@ -99,5 +99,7 @@ class Command(BaseCommand):
             self.first_iteration = False
             self.mail_fetcher.pull()
 
-        # Consume whatever files we can
-        self.file_consumer.run()
+        # Consume whatever files we can.
+        # We have to run twice as the first run checks for file readiness
+        for i in range(2):
+            self.file_consumer.run()