fix select_related and prefetch_related set in resolver getting lost

Author: jsurloppe

graphene_django/filter/fields.py

@@ -62,7 +62,7 @@ def merge_querysets(default_queryset, queryset):
         low = default_queryset.query.low_mark or queryset.query.low_mark
         high = default_queryset.query.high_mark or queryset.query.high_mark
         default_queryset.query.clear_limits()
-        queryset = default_queryset & queryset
+        queryset &= default_queryset
         queryset.query.set_limits(low, high)
         return queryset