Zen2ify testMasterFailoverDuringIndexingWithMappingChanges (#38178)

In Zen2 cluster bootstrap is required and some parameters are 
called differently in Zen2.

server/src/test/java/org/elasticsearch/action/support/master/IndexingMasterFailoverIT.java

@@ -23,7 +23,6 @@
 import org.elasticsearch.action.index.IndexResponse;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.discovery.DiscoverySettings;
-import org.elasticsearch.discovery.zen.ElectMasterService;
 import org.elasticsearch.discovery.zen.FaultDetection;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.test.ESIntegTestCase;
@@ -72,12 +71,12 @@ public void testMasterFailoverDuringIndexingWithMappingChanges() throws Throwabl
         final Settings sharedSettings = Settings.builder()
                 .put(FaultDetection.PING_TIMEOUT_SETTING.getKey(), "1s") // for hitting simulated network failures quickly
                 .put(FaultDetection.PING_RETRIES_SETTING.getKey(), "1") // for hitting simulated network failures quickly
-                .put(TestZenDiscovery.USE_ZEN2.getKey(), false)
-                .put("discovery.zen.join_timeout", "10s")  // still long to induce failures but to long so test won't time out
+                .put("cluster.join.timeout", "10s")  // still long to induce failures but not too long so test won't time out
                 .put(DiscoverySettings.PUBLISH_TIMEOUT_SETTING.getKey(), "1s") // <-- for hitting simulated network failures quickly
-                .put(ElectMasterService.DISCOVERY_ZEN_MINIMUM_MASTER_NODES_SETTING.getKey(), 2)
                 .build();
 
+        internalCluster().setBootstrapMasterNodeIndex(2);
+
         internalCluster().startMasterOnlyNodes(3, sharedSettings);
 
         String dataNode = internalCluster().startDataOnlyNode(sharedSettings);