Fix interaction with procrastinate

[voidus]

Running procrastinate subcommands when configurations is installed gives the following error:

> ./manage.py procrastinate healthchecks
Adding tasks from blueprint
Adding tasks from blueprint
healthchecks() got an unexpected keyword argument 'configuration'

The monkey-patching in create_parser caused this in an interesting way:

Procrastinate uses the add_arguments hook to check the previously defined arguments like this:

class Command(BaseCommand):
    def add_arguments(self, parser):
      self._django_options = {a.dest for a in parser._actions}
      ...

in order to later filter them out like this:

  def handle(self, *args, **kwargs):
    ...
    kwargs = {k: v for k, v in kwargs.items() if k not in self._django_options}
    ...

This is a problem because the CONFIGURATION_ARGUMENT arg is added after procrastinate's add_arguments is called. Here's the call graph:

  create_parser (django-configurations)
  -> create_parser (django) (a.k.a. orig_create_parser)
    -> add_arguments (procrastinate)
    -> (CONFIGURATION_ARGUMENT added here)

This commit esesentially swaps the inner two actions so it looks like this:

  create_parser (django-configurations)
  -> create_parser (django) (a.k.a. orig_create_parser)
    -> (CONFIGURATION_ARGUMENT added here)
    -> add_arguments (procrastinate)

It does this by temporarily overriding add_arguments with a no-op and then later restoring and calling it.

This is a hack on top of two hacks, but I can't really see any other ways to make it work.