bibdocfile: better temporary files for bibupload
bibdocfile: better temporary files for bibupload

* BibDocFile CLI tool usually prepares some MARCXML that is passed
  to BibUpload. For this, a temporary file is created under CFG_TMPDIR.
  The algorithm to choose the name was causing clashes when bibdocfile
  was called more than once per second. This is fixed now by using
  mkstemp.

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