Skip prevoting if single-node discovery (#91255)

Fixes #89867

Author: kingherc

server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java

@@ -1628,6 +1628,10 @@ public void run() {
                         }
 
                         if (prevotingRound != null) {
+                            if (singleNodeDiscovery) {
+                                logger.debug("skip prevoting as single-node discovery is enabled");
+                                return;
+                            }
                             prevotingRound.close();
                         }
                         prevotingRound = preVoteCollector.start(lastAcceptedState, getDiscoveredNodes());

test/framework/src/main/java/org/elasticsearch/cluster/coordination/AbstractCoordinatorTestCase.java

@@ -208,7 +208,7 @@ protected static int defaultInt(Setting<Integer> setting) {
         return setting.get(Settings.EMPTY);
     }
 
-    // Updating the cluster state involves up to 7 delays:
+    // Updating the cluster state involves up to the following number of delays:
     // 1. submit the task to the master service
     // 2. state publisher task on master
     // 3. master sends out PublishRequests to nodes