BibFormat: fixes unit tests
BibFormat: fixes unit tests

* FormatTest failed to append CFG_TMPDIR to sys.path and resulted
  in tests failing under some conditions. (closes #1320)

Reviewed-by: Tibor Simko <c7116e45300b163846dc01f3ed02116e3f8ef7a5@cern.ch>

inveniosoftware/invenio-formatter,tiborsimko/invenio-formatter,tiborsimko/invenio-formatter,inveniosoftware/invenio-formatter,inveniosoftware/invenio-formatter,tiborsimko/invenio-formatter