policy-node.lua: fix param name typo when finding target

Fixes unespected issues when finding first available target
2 jobs for policy-node-fix in 1 minute and 2 seconds (queued for 1 second)
Status Job ID Name Coverage
  Container
passed #8586558
container_fedora

00:00:15

 
  Build
passed #8586559
build_on_fedora

00:00:47