Fix bug in ChatterController, posts and discussions ordering

[terdia]

A discussion should be ordered by posts and discussions instead of discussions and discussions

Issue: Currently order by posts in config has no effect because the order by clause uses chatter.order_by.discussions.by and chatter.order_by.discussions.by

Fix: update order by clause to use chatter.order_by.posts.order and chatter.order_by.discussions.by

[marktopper]

chatter.order_by.discussions.order is used for sorting the list of discussions while chatter.order_by.posts.order is used to order the posts inside a discussion. Please do not mix the two.

[terdia]

@marktopper I am not missing the two, what I am saying his posts.order is not used in the code you only used discussions twice, correct me if I am wrong

[marktopper]

It's used here.