Fixed a bug where when shield is disabled it still replaced the transport

Closes elastic/elasticsearch#430

Original commit: elastic/x-pack-elasticsearch@422ba76d81

src/main/java/org/elasticsearch/shield/ShieldModule.java

@@ -28,7 +28,6 @@ public class ShieldModule extends AbstractShieldModule.Spawn {
         super(settings);
     }
 
-
     @Override
     public Iterable<? extends Module> spawnModules(boolean clientMode) {
         // spawn needed parts in client mode

src/main/java/org/elasticsearch/shield/ShieldPlugin.java

@@ -51,7 +51,9 @@ public class ShieldPlugin extends AbstractPlugin {
 
     @Override
     public Collection<Class<? extends Module>> modules() {
-        return ImmutableList.<Class<? extends Module>>of(ShieldModule.class);
+        return enabled ?
+                ImmutableList.<Class<? extends Module>>of(ShieldModule.class) :
+                ImmutableList.<Class<? extends Module>>of();
     }
 
     @Override

src/test/java/org/elasticsearch/shield/ShieldPluginEnabledDisabledTests.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.shield;
+
+import org.elasticsearch.common.settings.ImmutableSettings;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.shield.transport.SecuredTransportService;
+import org.elasticsearch.shield.transport.netty.NettySecuredTransport;
+import org.elasticsearch.test.ElasticsearchIntegrationTest.ClusterScope;
+import org.elasticsearch.test.ShieldIntegrationTest;
+import org.elasticsearch.transport.Transport;
+import org.elasticsearch.transport.TransportService;
+import org.hamcrest.Matcher;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.elasticsearch.test.ElasticsearchIntegrationTest.Scope.SUITE;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.not;
+
+/**
+ *
+ */
+@ClusterScope(scope = SUITE)
+public class ShieldPluginEnabledDisabledTests extends ShieldIntegrationTest {
+
+    private static boolean enabled;
+
+    @BeforeClass
+    public static void init() {
+        enabled = randomBoolean();
+    }
+
+    @Override
+    protected Settings nodeSettings(int nodeOrdinal) {
+        logger.info("******* shield is " + (enabled ? "enabled" : "disabled"));
+        return ImmutableSettings.settingsBuilder()
+                .put(super.nodeSettings(nodeOrdinal))
+                .put("shield.enabled", enabled)
+                .build();
+    }
+
+    @Override
+    protected Settings transportClientSettings() {
+        return ImmutableSettings.settingsBuilder()
+                .put(super.transportClientSettings())
+                .put("shield.enabled", enabled)
+                .build();
+    }
+
+    @Test @SuppressWarnings("unchecked")
+    public void testEnabledDisabled() throws Exception {
+        for (TransportService service : internalCluster().getInstances(TransportService.class)) {
+            Matcher matcher = instanceOf(SecuredTransportService.class);
+            if (!enabled) {
+                matcher = not(matcher);
+            }
+            assertThat(service, matcher);
+        }
+        for (Transport transport : internalCluster().getInstances(Transport.class)) {
+            Matcher matcher = instanceOf(NettySecuredTransport.class);
+            if (!enabled) {
+                matcher = not(matcher);
+            }
+            assertThat(transport, matcher);
+        }
+    }
+}