Fix tests depending on _ilm/status API

Since elastic#129367 we run the `_ilm/status` API on the local node, which
could cause issues in tests that assume the API runs on the master node
(i.e. they assumed that once the assertion passed, all nodes in the
cluster would have that cluster state, which is not true).

Author: nielsbauman

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestCase.java

@@ -1056,7 +1056,7 @@ private void wipeCluster() throws Exception {
         deleteAllNodeShutdownMetadata();
     }
 
-    private void waitForClusterUpdates() throws Exception {
+    public void waitForClusterUpdates() throws Exception {
         logger.info("Waiting for all cluster updates up to this moment to be processed");
 
         try {

x-pack/plugin/ilm/qa/multi-node/src/javaRestTest/java/org/elasticsearch/xpack/MigrateToDataTiersIT.java

@@ -169,6 +169,8 @@ public void testMigrateToDataTiersAction() throws Exception {
             Response response = client().performRequest(new Request("GET", "_ilm/status"));
             assertThat(EntityUtils.toString(response.getEntity()), containsString(OperationMode.STOPPED.toString()));
         });
+        // Wait for cluster state to be published to all nodes.
+        waitForClusterUpdates();
 
         String indexWithDataWarmRouting = "indexwithdatawarmrouting";
         Settings.Builder settings = Settings.builder()
@@ -340,6 +342,8 @@ public void testIndexTemplatesMigration() throws Exception {
                 Response response = client().performRequest(new Request("GET", "_ilm/status"));
                 assertThat(EntityUtils.toString(response.getEntity()), containsString(OperationMode.STOPPED.toString()));
             });
+            // Wait for cluster state to be published to all nodes.
+            waitForClusterUpdates();
         }
 
         Request migrateRequest = new Request("POST", "_ilm/migrate_to_data_tiers");

x-pack/plugin/ilm/qa/multi-node/src/javaRestTest/java/org/elasticsearch/xpack/ilm/TimeSeriesLifecycleActionsIT.java

@@ -766,6 +766,8 @@ public void testCanStopILMWithPolicyUsingNonexistentPolicy() throws Exception {
             String status = (String) statusResponseMap.get("operation_mode");
             assertEquals("STOPPED", status);
         });
+        // Wait for cluster state to be published to all nodes.
+        waitForClusterUpdates();
 
         // Re-start ILM so that subsequent tests don't fail
         Request startILMRequest = new Request("POST", "_ilm/start");