introduce new job state, MAX_RETRIED

Currently, when a job's retry_count reaches/exceeds max_retry count, we
do not update the job status to denote that the job has failed. As a
result there is no way to send job.failed notification.

This patch addresses the issue by introducing a new job status,
'MAX_RETRIED' which will get updated whenever a job's retry_count
reaches/exceeds max_retry.
Some of the key changes done as part of the patch are as follows:
- moved the config param 'max_retry' from qonos-api.conf to
  qonos-worker.conf.
- made the job processor on qonos-worker responsible for validating the
  max_retry count and based on that update the job status
- made changes to the '_job_get_next_by_action' query to ignore jobs
  whose status are set to 'MAX_RETRIED' and also removed the criteria
that checks if the job's retry_count is lesser than max_retry
- removed the job.failed notification logic from qonos.api.jobs.
- made the job.failed notification for 'MAX_RETRIED' to be sent by
  qonos-worker.