Pipeline processor is disregarded if configured to be after message filter chain in "Message Processors Configuration"

Graylog v2.3.0+81f8228 + Ubuntu 16.04

## Expected Behavior
The rules and such within the pipelines should be processed, but they are not, or perhaps the results merely not assigned to the message.

## Current Behavior
If I have the pipeline processor configured as #1 in the list, all is well...
Anything else, I see messages get sent to the pipelines, but seemingly nothing is processed. Put the pipeline processor as #1 in the list, and everything works as expected.

* Graylog Version: Graylog v2.3.0+81f8228
* Elasticsearch Version: 5.5
* MongoDB Version: v2.6.10
* Operating System: Ubuntu 16.04
* Browser version: (not a browser bug - all)