WORKER_NODES_COUNT indexed is not the number of workers used in the test

[afcollins]

When running the node-density* workloads of kube-burner, if I specify a NODE_COUNT that is smaller than the number of available workers, that test parameter value is not indexed. Instead, the totale number of workers available is indexed.

This could be part of a (larger?) ask to index the test parameters for future reference.