arxiv: OAI query fix

• FIX Adds proper quotation around OAI-PMH query to avoid a query parser exception due to colons in the OAI identifiers.

Reviewed-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>