BatchUploader: fix retrieval of recs from extoaiid
BatchUploader: fix retrieval of recs from extoaiid

* Does necessary corrections in order to treat the result of
  find_records_from_extoaiid() as an intbitset and not a recid.
  (closes #621)

tiborsimko/invenio,inveniosoftware/invenio,tiborsimko/invenio,inveniosoftware/invenio