BibDocFile: duplicate docname fix

* Fixes an issue when checking duplicate docnames in the
  BibDocFile client that caused a false alert.  (PR #1930)

* Fixes the report output which had the wrong order of arguments.

Reported-by: Alexander Wagner <a.wagner@fz-juelich.de>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>