uploader: refactoring of workflow definition

* Refactors the "insert" workflow definitions to conform with
  the standard pattern of workflows. This will also avoid the current
  issue that the workflows registry has the "insert" workflow with key
  None.

Acked-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
Acked-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>