Lumberjack + multiline codec is not worker thread safe and does not actually support multiline

[blipper]

Basic issues

1. Lumberjback + Multiline codec don't play well together.
2. Lumberjack doesn't support stream_identity
3. Even if it did multiline codec isn't safe with worker threads if you implement number 2 above

Ugly Workaround below fixes #1-#3

• Derives stream_identity from host:port
• Mutexes the buffer hash
• Breaks other codecs that you might be using

blipper@9b54c21

Not sure what the real fix is this works for us

[suyograo]

Fix in logstash-plugins/logstash-input-lumberjack#5