pluginutils: fix for failing bibformat test case
pluginutils: fix for failing bibformat test case

* Fixes broken test case caused by 'dummy_' variable prefix
  which made the pluginbuilder's function-signature incompatible
  with the bibformat elements.

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