`values[:includes]` in `reflection_scope` is not compatible with `through_scope`

Without this fix, preloading `:comments_with_include` will cause the
following error:

```
% bundle exec ruby -w -Itest test/cases/associations/eager_test.rb -n test_eager_with_has_many_through_join_model_with_include
Using sqlite3
Run options: -n test_eager_with_has_many_through_join_model_with_include --seed 1502

E

Error:
EagerAssociationTest#test_eager_with_has_many_through_join_model_with_include:
ActiveRecord::AssociationNotFoundError: Association named 'post' was not found on Post; perhaps you misspelled it?
```

1 files changed, 1 insertions, 1 deletions

diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 09958ca257..025d013fb4 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -21,7 +21,7 @@ class Author < ActiveRecord::Base
   end
   has_many :comments_containing_the_letter_e, through: :posts, source: :comments
   has_many :comments_with_order_and_conditions, -> { order("comments.body").where("comments.body like 'Thank%'") }, through: :posts, source: :comments
-  has_many :comments_with_include, -> { includes(:post) }, through: :posts, source: :comments
+  has_many :comments_with_include, -> { includes(:post).where(posts: { type: "Post" }) }, through: :posts, source: :comments
 
   has_many :first_posts
   has_many :comments_on_first_posts, -> { order("posts.id desc, comments.id asc") }, through: :first_posts, source: :comments