workflows: refactoring of holdingpen

* Implements caching for fast research sorting and else.

* Simplifies the code.

* Factorizes some code part.

Signed-off-by: Guillaume Lastecoueres <guillaume.lastecoueres@cern.ch>
workflows: remove view test

* Removes the view test as it does not test anything as the
  page requires login and it has different behavior if DEBUG
  mode is available and thus fails (200 vs 401). This can create
  confusion when developing.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>