oaiharvest: fixes harvest() web interface

* Adds missing parameters in oaiharvestadmin.harvest() function
  causing errors in the webinterface handler.
  (PR #2524)

Acked-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>