Sending data to Graylog is broken

[vkarak]

Currently, when using a Graylog handler, no data is transferred. This has been introduced with #1600 and specifically with commit: b30b250

[vkarak]

The problem is that with the changes introduced by #1600 we set up the extras inside the Formatter. This does not work for the pygelf handler, because it doesn't use a formatter at all.