Keep original queryset on DjangoFilterConnectionField

The PR #796 broke DjangoFilterConnectionField making it always get the
raw queryset from the model to apply the filters in it.

This makes sure that the DjangoObjectType's .get_queryset is called,
keeping any filtering it might have made.

Author: bellini666

graphene_django/filter/fields.py

@@ -55,9 +55,10 @@ def filtering_args(self):
     def resolve_queryset(
         cls, connection, iterable, info, args, filtering_args, filterset_class
     ):
+        qs = super().resolve_queryset(connection, iterable, info, args)
         filter_kwargs = {k: v for k, v in args.items() if k in filtering_args}
         return filterset_class(
-            data=filter_kwargs, queryset=iterable, request=info.context
+            data=filter_kwargs, queryset=qs, request=info.context
         ).qs
 
     def get_queryset_resolver(self):