**Build scan:**
https://gradle-enterprise.elastic.co/s/bcxstpjolnb2q/tests/:x-pack:plugin:ccr:internalClusterTest/org.elasticsearch.xpack.ccr.FollowerFailOverIT/testReadRequestsReturnLatestMappingVersion

**Reproduction line:**
```
./gradlew ':x-pack:plugin:ccr:internalClusterTest' --tests "org.elasticsearch.xpack.ccr.FollowerFailOverIT.testReadRequestsReturnLatestMappingVersion" -Dtests.seed=A75C1F0C6F541957 -Dtests.locale=fr-CA -Dtests.timezone=America/Tijuana -Druntime.java=20
```

**Applicable branches:**
8.10

**Reproduces locally?:**
Didn't try

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.ccr.FollowerFailOverIT&tests.test=testReadRequestsReturnLatestMappingVersion

**Failure excerpt:**
```
com.carrotsearch.randomizedtesting.UncaughtExceptionError: Captured an uncaught exception in thread: Thread[id=498, name=elasticsearch[follower2][clusterApplierService#updateTask][T#1], state=RUNNABLE, group=TGRP-FollowerFailOverIT]

  at __randomizedtesting.SeedInfo.seed([A75C1F0C6F541957:A564CB31A58082CC]:0)

  Caused by: java.lang.AssertionError: (No message provided)

    at __randomizedtesting.SeedInfo.seed([A75C1F0C6F541957]:0)
    at org.elasticsearch.discovery.PeerFinder.closePeers(PeerFinder.java:182)
    at org.elasticsearch.cluster.coordination.Coordinator.onClusterStateApplied(Coordinator.java:415)
    at org.elasticsearch.cluster.coordination.Coordinator.lambda$handleApplyCommit$8(Coordinator.java:403)
    at org.elasticsearch.action.ActionListenerImplementations$MappedActionListener.lambda$map$0(ActionListenerImplementations.java:108)
    at org.elasticsearch.action.ActionListenerImplementations$MappedActionListener.onResponse(ActionListenerImplementations.java:89)
    at org.elasticsearch.cluster.service.ClusterApplierService$ClusterApplyActionListener.onResponse(ClusterApplierService.java:598)
    at org.elasticsearch.cluster.service.ClusterApplierService$ClusterApplyActionListener.onResponse(ClusterApplierService.java:569)
    at org.elasticsearch.cluster.service.ClusterApplierService.runTask(ClusterApplierService.java:439)
    at org.elasticsearch.cluster.service.ClusterApplierService$UpdateTask.run(ClusterApplierService.java:154)
    at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:916)
    at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:217)
    at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:183)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    at java.lang.Thread.run(Thread.java:1623)

```
server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
logger.warn(
                                """
                                    This node is a fully-formed single-node cluster with cluster UUID [{}], but it is configured as if to \
                                    discover other nodes and form a multi-node cluster via the [{}={}] setting. Fully-formed clusters do \
                                    not attempt to discover other nodes, and nodes with different cluster UUIDs cannot belong to the same \
                                    cluster. The cluster UUID persists across restarts and can only be changed by deleting the contents of \
                                    the node's data path(s). Remove the discovery configuration to suppress this message.""",
                                applierState.metadata().clusterUUID(),
                                DISCOVERY_SEED_HOSTS_SETTING.getKey(),
                                DISCOVERY_SEED_HOSTS_SETTING.get(settings)
                            );
                        }
                    }
                    @Override
                    public String toString() {
                        return "single-node cluster checker";
                    }
                }, singleNodeClusterSeedHostsCheckInterval, clusterCoordinationExecutor);
            }
            return;
        }
        
        if (singleNodeClusterChecker != null) {
            singleNodeClusterChecker.cancel();
            singleNodeClusterChecker = null;
        }
    }
    void becomeCandidate(String method) {
        assert Thread.holdsLock(mutex) : "Coordinator mutex not held";
        logger.debug(