bibupload: get_record dog-piling prevention
bibupload: get_record dog-piling prevention

* Prevents dog-piling behavior when multiple processes call get_record
  and no cache exists (i.e. each process will try to generate the
  cache and save it).

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>

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