Default ES retention 50% on non-sensors

[petiepooo]

On nodes that do not store sensor data, the default elasticsearch.retention.retention_pct pillar remains at 50%, leaving much of the space unused unless explicitly updated after install. This used to be automatically updated to 80% on the v2.3 series.

Please see #12944 for a proposed solution.

[petiepooo]

(above edited to replace PR within my repo to PR submitted to your repo)