Test: ZenUnicastDiscoveryTests.testNormalClusterForming should start unicast hosts first

The test starts a cluster with random nodes as unicast hosts but *doesn't* use min_master_nodes. If the unicast hosts are started last, nodes may elect themselves as master as they do not have mechanism yet to share information.

src/test/java/org/elasticsearch/discovery/ZenUnicastDiscoveryTests.java

@@ -52,10 +52,19 @@ public class ZenUnicastDiscoveryTests extends ElasticsearchIntegrationTest {
     @Test
     public void testNormalClusterForming() throws ExecutionException, InterruptedException {
         int currentNumNodes = randomIntBetween(3, 5);
-        int currentNumOfUnicastHosts = randomIntBetween(1, currentNumNodes);
-        discoveryConfig = new ClusterDiscoveryConfiguration.UnicastZen(currentNumNodes, currentNumOfUnicastHosts);
 
-        internalCluster().startNodesAsync(currentNumNodes).get();
+        // use explicit unicast hosts so we can start those first
+        int[] unicastHostOrdinals = new int[randomIntBetween(1, currentNumNodes)];
+        for (int i = 0; i < unicastHostOrdinals.length; i++) {
+            unicastHostOrdinals[i] = i;
+        }
+        discoveryConfig = new ClusterDiscoveryConfiguration.UnicastZen(currentNumNodes, unicastHostOrdinals);
+
+        // start the unicast hosts
+        internalCluster().startNodesAsync(unicastHostOrdinals.length).get();
+
+        // start the rest of the cluster
+        internalCluster().startNodesAsync(currentNumNodes - unicastHostOrdinals.length).get();
 
         if (client().admin().cluster().prepareHealth().setWaitForNodes("" + currentNumNodes).get().isTimedOut()) {
             logger.info("cluster forming timed out, cluster state:\n{}", client().admin().cluster().prepareState().get().getState().prettyPrint());