CBQE-1233: adding raw task publisher method

This method assembles celery tasks and publishes them
to workers listening to any broker

Change-Id: I15e2d0d80e59f6b2abadda508e0914c716075007
Reviewed-on: http://review.couchbase.org/25802
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>