This patch adds a beanstalk CDR backend.

Beanstalkd is a simple to use job queue. It provides a means to
create multiple job queues called "tubes". Each tube can store
multiple jobs, with varying priorities with the queue. Queue
processing is available via a simple TCP socket or via well defined
libraries, avaialble at
https://github.com/kr/beanstalkd/wiki/client-libraries

This module is based upon the beanstalk-client library, available
for download at: https://github.com/deepfryed/beanstalk-client

Change-Id: I5fe4089a34ab3b39230786d9bbfddafa56715f48