* CI: add no_proxy regression test
* proxy: Fix the no_proxy variable
Since 2.29, probably due to a change in ansible templating, the no_proxy
variable is rendered as an array of character rather than a string.
This results in broken cluster in some case.
Eliminate the custom jinja looping to use filters and list flatteing +
join instead.
Also simplify some things (no separate tasks file, just use `run_once`
instead of delegating to localhost)
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Co-authored-by: Max Gautier <mg@max.gautier.name>
