implement 'qonos.job.failed' notification.

This patch includes the following changes:
- introduce a new notification event called 'qonos.job.failed'.
- send job info as payload with the notification.
- refactor process_job() method catch Polling and any other Exception and
  handle them by updating the job status as 'ERROR' and send
'qonos.job.failed' notification for the failed job.

Related to RM 4647

Co-authored-by: Sridevi Koushik <sridevi.koushik@rackspace.com>