Remove CurrentUser.ip_addr.

Remove the `CurrentUser.ip_addr` global variable and replace it with
`request.remote_ip`. Before we had to track the current user's IP in a
global variable so that when we edited a post for example, we could pass
down the user's IP to the model and save it in the post_versions table.
Now that we now longer save IPs in version tables, we don't need a global
variable to get access to the current user's IP outside of controllers.

app/logical/bulk_update_request_processor.rb

@@ -184,7 +184,7 @@ class BulkUpdateRequestProcessor
 
   # Process the bulk update request immediately.
   def process!
-    CurrentUser.scoped(User.system, "127.0.0.1") do
+    CurrentUser.scoped(User.system) do
       commands.map do |command, *args|
         case command
         when :create_alias