[develop] Avoid duplication of nodes in ClusterManager._find_active_nodes()#538

jdeamicis merged 3 commits intoaws:developaws/aws-parallelcluster-node:developfrom

jdeamicis:fix/devel/fix_nodelists_multiple_partitionsjdeamicis/aws-parallelcluster-node:fix/devel/fix_nodelists_multiple_partitionsCopy head branch name to clipboard