* Pass FORCE_SCRIPT_NAME to Daphne server when set
FORCE_SCRIPT_NAME seems not to be honored any more with build-in runserver after activating channels app.
The normal behavior of Django is the FORCE_SCRIPT_NAME is used as prefix when set while generating URLs so its possible to
create a path prefix and determine different Django installations based on the path rather than hostname without having to prefix all paths in urls.py.
* Only strip script_name from path if it starts with it
* make tests happy again after setting kwarg root_path
