Refactor logstash_worker into log_processor module

Separate the jenkins log client and worker bits into a new module
called log_processor with ::client and ::worker classes.

Instantiate two workers on each logstash worker node.

Change-Id: I7cfec410983c25633e6b555f22a85e9435884cfb
Merge "Refactor logstash_worker into log_processor module"