minor refactoring of AsyncAction

Signed-off-by: Pranshu Shukla <[email protected]>

server/src/main/java/org/opensearch/action/support/nodes/TransportNodesAction.java

@@ -239,20 +239,18 @@ class AsyncAction {
                 assert request.concreteNodes() != null;
             }
             this.responses = new AtomicReferenceArray<>(request.concreteNodes().length);
+            this.concreteNodes = request.concreteNodes();
 
             if (request.sendDiscoveryNodes() == false) {
-                // We transfer the ownership of discovery nodes to route the request to into the AsyncAction class.
-                // This reduces the payload of the request and improves the number of concrete nodes in the memory
-                this.concreteNodes = request.concreteNodes();
+                // As we transfer the ownership of discovery nodes to route the request to into the AsyncAction class, we
+                // remove the list of DiscoveryNodes from the request. This reduces the payload of the request and improves
+                // the number of concrete nodes in the memory.
                 request.setConcreteNodes(null);
-            } else {
-                // initializing it separately as we keep the `concreteNodes` as final since we want it to be immutable.
-                this.concreteNodes = null;
             }
         }
 
         void start() {
-            final DiscoveryNode[] nodes = request.concreteNodes() != null ? request.concreteNodes() : concreteNodes;
+            final DiscoveryNode[] nodes = this.concreteNodes;
             if (nodes.length == 0) {
                 // nothing to notify
                 threadPool.generic().execute(() -> listener.onResponse(newResponse(request, responses)));