Fix 'No permissions' error in Make_Movie.py. See #12227

This fixes https://trac.openmicroscopy.org.uk/ome/ticket/12227

To test, try running Make_Movie script (this will have to be locally since mencoder isn't installed on trout https://trello.com/c/0thKrlX5/449-mencoder-on-trout). The movie should be uploaded to OMERO as a file annotation and returned.