QUADs daemon - Deprecate heavy use of cron

[jtaleric]

Using the QUADs daemon we could spawn a worker thread on an interval (60 minute?), this thread could check the current schedule.

This worker could check if there are hosts to :

• Move
• Validate
• Post-Deploy
• ETC

[sadsfae]

Related RFE here in Milestones 1.1 and 2.0 (address same features)

#140
#156

[sadsfae]

We'll need a proper messagebus / worker architecture here. I've re-purposed #140 and #156 to tackle the more immediate enhancements we need to get there first.

Something like Celery / RabbitMQ may be what we're after long-term to become event-driven and not need to have cron in the mix.

[sadsfae]

We're looking into celery and in some cases asyncio for this since we're on Python3 now with 1.1. Keeping this open and targeted for 2.0 milestone.

[grafuls]

Been doing some research on this and I think celery might be a bit of an overkill as we would require a broker and a backend (Redis for both) for it to run and the scope of celery is more for long running async tasks on a queue which we might not take full advantage of with the Quads workflow.
There are several other tools we can use instead like python3-APScheduler which is available via rpm or the less available schedule or the python standard library sched.