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

@@ -55,10 +55,11 @@ def filtering_args(self):
     def resolve_queryset(
         cls, connection, iterable, info, args, filtering_args, filterset_class
     ):
+        qs = super(DjangoFilterConnectionField, cls).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
-        ).qs
+        return filterset_class(data=filter_kwargs, queryset=qs, request=info.context).qs
 
     def get_queryset_resolver(self):
         return partial(