Change number of Elastic/Opensearch nodes to support quorum

[williamtrelawny]

Currently, the script creates 2 Elastic/Opensearch nodes, which does not allow the cluster to achieve a quorum, unless only 1 node is deemed master-eligible and the other not. However, this would not result in a true cluster, which I believe is one of the goals of this script.

Number of Open/Elasticsearch nodes should be set to 3, and all should be master-eligible (which is default config I believe), so a proper cluster with quorum can be established.