This patch makes Celery to connect to RabbitMQ directly instead
of using LB. It also brings a forked version of a transport url
template, the reason for this is the format for Kombu/Celery
broker url is different from oslo_messaging transport url:
1. URLs need to be separated with semicolons vs commas.
2. Every item in Kombu broker url needs to be a complete url
that includes schema, vhost, and all credentials.
This format is specific to Airflow and is not used in upstream
OSH projects, hence it is included here and not in htk.