track(merged): Fix: Select iptables backend by kernel module, fail loud on misprogram (ext#518)

Tracking stub for **merged PR kagenti-extensions#518** — auto-created so it rolls up as completed work under epic #1429.

https://github.com/kagenti/kagenti-extensions/pull/518

_Closed because the PR is already merged. Label `epic-progress` marks auto-created trackers._