Allow output plugins to declare that, for a given configuration, workers are
not supported. Such reasons could include inability to share a resource
(like a listening socket, etc). This declaration will force a
single-worker setting and allow logstash to warn the user instead of
aborting.
- Include a (hopefully) better warning message when using an output
plugin that doesn't support workers.
- Remove worker_setup_skip hackery; not needed.
- update file and zeromq workers_not_supported settings
Be more obvious that worker count is ignored but otherwise work will continue
tcp in server mode doesn't support workers.
Merge pull request #732 from logstash/output-workers-not-supported

Allow output plugins to declare that, for a given configuration, workers...