Fix Bug causing DjangoFilterConnectionField to ignore annotations, .reverse() and

[BossGrand]

other queryset modifications being applied in resolvers.

the actual fix is really small.

In DjangoFilterConnectionField.merge_querysets default_queryset was overriding queryset.

if you look at DjangoConnectionField.merge_querysets you can see it was doing this merge correctly.

@classmethod
    def merge_querysets(cls, default_queryset, queryset):
        return queryset & default_queryset 

So this pr simply changes DjangoFilterConnectionField merge to match DjangoConnectionField merge. Along with a couple of tests

[BossGrand]

Closing because I realized I accidentally rolled in a different pull request into this

[coveralls]

Coverage increased (+0.01%) to 93.014% when pulling aa55a86 on BossGrand:fix/dj_filter_conn_field_merge_queries into 2600f0f on graphql-python:master.