No logs generated for "JSON Path from HTTP API" input

## Expected Behavior
There should be something in the logs when the JSON Path from HTTP API input runs, especially if it is not running successfully.

## Current Behavior
When trying to troubleshoot issues with JSON Path from HTTP API input, no logs exist except for the log that the input has started. No indication of if the API call is being made, and if so, what the response is.

## Steps to Reproduce (for bugs)

1. Create JSON Path from HTTP API input
2. (In my case did not receive logs on the input as expected)
3. Check server.log
4. Only entry is for input starting.

## Context
@kroepke requested a submit a bug report for this issue as he concurs this should be logged in some way.

## Your Environment

* Graylog Version: 3.0.1
* Elasticsearch Version:
* MongoDB Version:
* Operating System: Ubunutu 18.04
* Browser version: