Fix IndexStatsIT#testFilterCacheStats

Verify that the global checkpoint actually got synced with the in-memory version
in an `assertBusy` block.

Resolve #124447

Author: arteam

server/src/internalClusterTest/java/org/elasticsearch/indices/stats/IndexStatsIT.java

@@ -58,7 +58,6 @@
 import org.elasticsearch.test.ESIntegTestCase.ClusterScope;
 import org.elasticsearch.test.ESIntegTestCase.Scope;
 import org.elasticsearch.test.InternalSettingsPlugin;
-import org.elasticsearch.test.junit.annotations.TestLogging;
 import org.elasticsearch.xcontent.XContentType;
 
 import java.io.IOException;
@@ -1095,7 +1094,6 @@ private void assertCumulativeQueryCacheStats(IndicesStatsResponse response) {
         assertEquals(total, shardTotal);
     }
 
-    @TestLogging(value = "org.elasticsearch.cluster.service:TRACE", reason = "https://github.com/elastic/elasticsearch/issues/124447")
     public void testFilterCacheStats() throws Exception {
         Settings settings = Settings.builder()
             .put(indexSettings())
@@ -1370,10 +1368,12 @@ private void persistGlobalCheckpoint(String index) throws Exception {
             for (IndexService indexService : indexServices) {
                 for (IndexShard indexShard : indexService) {
                     indexShard.sync();
-                    assertThat(
-                        "Routing entry for shard " + indexShard.routingEntry().toString(),
-                        indexShard.getLastSyncedGlobalCheckpoint(),
-                        equalTo(indexShard.getLastKnownGlobalCheckpoint())
+                    assertBusy(
+                        () -> assertThat(
+                            "Routing entry for shard " + indexShard.routingEntry().toString(),
+                            indexShard.getLastSyncedGlobalCheckpoint(),
+                            equalTo(indexShard.getLastKnownGlobalCheckpoint())
+                        )
                     );
                 }
             }