Guard checking master node watching for file settings (#124960)

Author: rjernst

server/src/internalClusterTest/java/org/elasticsearch/reservedstate/service/FileSettingsServiceIT.java

@@ -253,7 +253,7 @@ public void testSettingsApplied() throws Exception {
 
         FileSettingsService masterFileSettingsService = internalCluster().getInstance(FileSettingsService.class, masterNode);
 
-        assertTrue(masterFileSettingsService.watching());
+        assertBusy(() -> assertTrue(masterFileSettingsService.watching()));
         assertFalse(dataFileSettingsService.watching());
 
         writeJSONFile(masterNode, testJSON, logger, versionCounter.incrementAndGet());
@@ -279,7 +279,7 @@ public void testSettingsAppliedOnStart() throws Exception {
 
         FileSettingsService masterFileSettingsService = internalCluster().getInstance(FileSettingsService.class, masterNode);
 
-        assertTrue(masterFileSettingsService.watching());
+        assertBusy(() -> assertTrue(masterFileSettingsService.watching()));
         assertFalse(dataFileSettingsService.watching());
 
         assertClusterStateSaveOK(savedClusterState.v1(), savedClusterState.v2(), "50mb");
@@ -374,7 +374,7 @@ public void testErrorSaved() throws Exception {
 
         FileSettingsService masterFileSettingsService = internalCluster().getInstance(FileSettingsService.class, masterNode);
 
-        assertTrue(masterFileSettingsService.watching());
+        assertBusy(() -> assertTrue(masterFileSettingsService.watching()));
         assertFalse(dataFileSettingsService.watching());
 
         writeJSONFile(masterNode, testErrorJSON, logger, versionCounter.incrementAndGet());
@@ -470,7 +470,7 @@ public void testSettingsAppliedOnMasterReElection() throws Exception {
         var savedClusterState = setupClusterStateListener(masterNode);
         FileSettingsService masterFileSettingsService = internalCluster().getInstance(FileSettingsService.class, masterNode);
 
-        assertTrue(masterFileSettingsService.watching());
+        assertBusy(() -> assertTrue(masterFileSettingsService.watching()));
 
         writeJSONFile(masterNode, testJSON, logger, versionCounter.incrementAndGet());
         assertClusterStateSaveOK(savedClusterState.v1(), savedClusterState.v2(), "50mb");