arxiv: response code addition

* Avoids an error if a response message is not mapped with an HTTP
  code and returns original response status code.

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
records: fix for MarcXML indentation on creation

* Makes MarcXML more readable and properly indented.

Signed-off-by: Pedro Gaudêncio <pedro.gaudencio@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>