Because slapos.core hardcodes a "supervisord.socket", this file happens to be deleted and cause bugs

This solution is better than adding a sleep in a crontab, because it will be a new
date every day

Revert "resilient: new paramater to define the time to sleep before running the backup in the cron job."

This reverts commit 30d1a937.

It includes more debugging lines, not deploying a slapproxy (no need anymore thanks
the free-port selection recipe), and not delegating some work to a cron job.

In gunicorn v19.6 and v19.5, a bug was introduced which deletes socket when nginx worker exits.
In our case, it crashes the slaprunner and prevents it from restarting by slapos.
Let's stick to v19.4.5 until this issue is closed : https://github.com/benoitc/gunicorn/issues/1298

Default is a random value between 0 and 6 hours. KVM and Slaprunner test instances set it at 0.

In the case of hellorina SR, the following section generated invalid command:

[proxy]
command-line = {{ python_location }}/bin/python2.7 {{ rina_proxy }} ${server:instance-guid} ${:ipv6} ${:port}
...