Fix users list sorting

ActiveRecord doesn't notice that we need to join with `members` in two
parts of the ActiveRecord::Relation and it joins it two times adding
an alias called `members_users`, instead of joining that table just once.

As the constraint on the `organization_id` was referencing the
`members_users` table this wasn't picked up by Postgres while joining
the tables. Specifically, when joining `users` with `members`, thus
returning all members of a user, regardless of their organization.

app/controllers/users_controller.rb

@@ -2,13 +2,14 @@ class UsersController < ApplicationController
   before_filter :authenticate_user!
 
   def index
-    @search = current_organization.users.ransack(params[:q])
+    @search = User.ransack(params[:q])
     @search.sorts = 'members_member_uid asc' if @search.sorts.empty?
 
     @users = @search
       .result(distinct: false)
       .joins(members: :account)
       .eager_load(members: :account)
+      .where(members: { organization: current_organization.id })
       .page(params[:page])
       .per(25)