[httpjson] add option to silence complaints about null values

[msoltyspl]

Currently, whenever an explicit null value is encountered by httpjson - it always informs about it in the logs and there seems to be no way to turn it off, e.g.:

json parser ignoring pipelines_.monitoring-logstash_events
json parser ignoring pipelines_.monitoring-logstash_reloads_last_success_timestamp
json parser ignoring pipelines_.monitoring-logstash_reloads_last_failure_timestamp
json parser ignoring pipelines_.monitoring-logstash_reloads_last_error
json parser ignoring pipelines_.monitoring-logstash_queue
json parser ignoring pipelines_main_reloads_last_error
json parser ignoring pipelines_main_reloads_last_success_timestamp
json parser ignoring pipelines_main_reloads_last_failure_timestamp

So far I've been reloading (logstash) once with failed config and once with correct config to silence some of those messages, but that's a bit crude workaround. Explicit nulls are not technically invalid - so an option to just ignore those silently would be really welcome.

[danielnelson]

I think we should just silence this without providing an option. Here is some JSON input that will trigger this message: {"x": null}

[msoltyspl]

I think we should just silence this without providing an option. Here is some JSON input that will trigger this message: {"x": null}

Even better =)

[Fyyre]

Michal, I apologize for writing this way - but I lost your contact. Long time since last speak. Can you please get in touch with me at fyyre @ fyyre.ru ?

Thanks =)