[TEST] fixed unicast bw comp test configuration

The second internal node, when present, wasn't able to join the existing cluster due ti misconfigured unicast hosts, thus it would form its own cluster.

Author: javanna

src/test/java/org/elasticsearch/bwcompat/UnicastBackwardsCompatibilityTest.java

@@ -34,7 +34,7 @@ protected Settings nodeSettings(int nodeOrdinal) {
         return ImmutableSettings.builder()
                 .put("transport.tcp.port", 9380 + nodeOrdinal)
                 .put("discovery.zen.ping.multicast.enabled", false)
-                .put("discovery.zen.ping.unicast.hosts", "localhost:9390,localhost:9391")
+                .put("discovery.zen.ping.unicast.hosts", "localhost:9380,localhost:9381,localhost:9390,localhost:9391")
                 .put(super.nodeSettings(nodeOrdinal))
                 .build();
     }
@@ -44,13 +44,13 @@ protected Settings externalNodeSettings(int nodeOrdinal) {
         return ImmutableSettings.settingsBuilder()
                 .put("transport.tcp.port", 9390 + nodeOrdinal)
                 .put("discovery.zen.ping.multicast.enabled", false)
-                .put("discovery.zen.ping.unicast.hosts", "localhost:9380,localhost:9381")
+                .put("discovery.zen.ping.unicast.hosts", "localhost:9380,localhost:9381,localhost:9390,localhost:9391")
                 .put(super.nodeSettings(nodeOrdinal))
                 .build();
     }
 
     @Test
-    public void testUnicastDiscovery() throws Exception {
+    public void testUnicastDiscovery() {
         ClusterHealthResponse healthResponse = client().admin().cluster().prepareHealth().get();
         assertThat(healthResponse.getNumberOfDataNodes(), equalTo(cluster().numDataNodes()));
     }