When testing aggregate plugin get a ConfigurationError for a valid configuration

Filed a bug against `logstash-filter-aggregate` plugin but perhaps I should have filed it here. Have been struggling to test my logstash configurations using `logstash-devutils`. Testing based on this post https://gquintana.github.io/2016/09/07/Testing-Logstash-configuration.html . I define a valid logstash configuration, test it's validity via the logstash tool, run it, all good, etc.

When testing with `logstash-devutils` get a `ConfigurationError` but I am only defining one timeout. Even when slimming down my example shown in 119 to have only a single aggregate block in the filter section get the same error. It's really a shame because I was looking forward to learning more about the logstash development ecosystem. But I've lost many days trying to write simple tests.

```
Aggregate plugin: For task_id pattern '%{eventId}', there are more than one filter which defines timeout options. All timeout options have to be defined in only one aggregate filter per task_id pattern. Timeout options are : timeout, inactivity_timeout, timeout_code, push_map_as_event_on_timeout, push_previous_map_as_event, timeout_timestamp_field, timeout_task_id_field, timeout_tags
```

https://github.com/logstash-plugins/logstash-filter-aggregate/issues/119