title: Nginx module for filebeats doesn't parse access logs
body: <p>I am using nginx module for filebeats to send log data to elasticsearch. Here is my filebeats configuration:</p>
  
  <pre><code>output:
    logstash:
      enabled: true
      hosts:
        - logstash:5044
      timeout: 15
  
  filebeat.modules:
  - module: nginx
    access:
      enabled: true
      var.paths: ["/var/log/nginx/access.log"]
    error:
      enabled: true
      var.paths: ["/var/log/nginx/error.log"]
  </code></pre>
  
  <p>The problem is that logs are not parsed. This is what I see in Kibana:</p>
  
  <pre><code>{   "_index": "filebeat-2017.07.18",   "_type": "log",   "_id": "AV1VLXEbhj7uWd8Fgz6M",   "_version": 1,   "_score": null,   "_source": {
      "@timestamp": "2017-07-18T10:10:24.791Z",
      "offset": 65136,
      "@version": "1",
      "beat": {
        "hostname": "06d09033fb23",
        "name": "06d09033fb23",
        "version": "5.5.0"
      },
      "input_type": "log",
      "host": "06d09033fb23",
      "source": "/var/log/nginx/access.log",
      "message": "10.15.129.226 - - [18/Jul/2017:12:10:21 +0200] \"POST /orders-service/orders/v1/sessions/update/FUEL_DISPENSER?api_key=vgxt5u24uqyyyd9gmxzpu9n7 HTTP/1.1\" 200 5 \"-\" \"Mashery Proxy\"",
      "type": "log",
      "tags": [
        "beats_input_codec_plain_applied"
      ]   },   "fields": {
      "@timestamp": [
        1500372624791
      ]   },   "sort": [
      1500372624791   ] }
  </code></pre>
  
  <p>I am missing parsed fields, as specified in the documentation: <a href="https://www.elastic.co/guide/en/beats/filebeat/current/exported-fields-nginx.html" rel="nofollow noreferrer">https://www.elastic.co/guide/en/beats/filebeat/current/exported-fields-nginx.html</a></p>
  
  <p>Why are log lines not parsed?</p>