Upgrade to java8

- bump guava version to 21.0
- fix DimensionData test
diff --git a/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/features/NetworkApiMockTest.java b/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/features/NetworkApiMockTest.java
index 5002a8b..ba94b0f 100644
--- a/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/features/NetworkApiMockTest.java
+++ b/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/features/NetworkApiMockTest.java
@@ -259,7 +259,8 @@
 
    public void testListNatRules() throws Exception {
       server.enqueue(new MockResponse().setBody(payloadFromResource("/natRules.json")));
-      api().listNatRules("12345").concat().toList();
+      Iterable<NatRule> natRules = api().listNatRules("12345").concat().toList();
+      assertEquals(size(natRules), 2);
       assertSent(GET, "/caas/2.4/6ac1e746-b1ea-4da5-a24e-caf1a978789d/network/natRule?networkDomainId=12345");
    }
 
@@ -294,13 +295,15 @@
 
    public void testListFirewallRules() throws Exception {
       server.enqueue(new MockResponse().setBody(payloadFromResource("/firewallRules.json")));
-      api().listFirewallRules("12345").concat().toList();
+      Iterable<FirewallRule> firewallRules =  api().listFirewallRules("12345").concat().toList();
+      assertEquals(size(firewallRules), 1);
       assertSent(GET, "/caas/2.4/6ac1e746-b1ea-4da5-a24e-caf1a978789d/network/firewallRule?networkDomainId=12345");
    }
 
    public void testListFirewallRules_404() throws Exception {
       server.enqueue(response404());
-      api().listFirewallRules("12345").concat().toList();
+      Iterable<FirewallRule> firewallRules =  api().listFirewallRules("12345").concat().toList();
+      assertEquals(size(firewallRules), 0);
       assertSent(GET, "/caas/2.4/6ac1e746-b1ea-4da5-a24e-caf1a978789d/network/firewallRule?networkDomainId=12345");
    }
 
diff --git a/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/internal/BaseDimensionDataCloudControlApiLiveTest.java b/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/internal/BaseDimensionDataCloudControlApiLiveTest.java
index 85ce632..e682f34 100644
--- a/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/internal/BaseDimensionDataCloudControlApiLiveTest.java
+++ b/dimensiondata/src/test/java/org/jclouds/dimensiondata/cloudcontrol/internal/BaseDimensionDataCloudControlApiLiveTest.java
@@ -40,7 +40,7 @@
 import java.util.Properties;
 import java.util.Set;
 
-import static com.google.common.util.concurrent.MoreExecutors.sameThreadExecutor;
+import static com.google.common.util.concurrent.MoreExecutors.newDirectExecutorService;
 import static org.jclouds.dimensiondata.cloudcontrol.config.DimensionDataCloudControlComputeServiceContextModule.NETWORK_DOMAIN_DELETED_PREDICATE;
 import static org.jclouds.dimensiondata.cloudcontrol.config.DimensionDataCloudControlComputeServiceContextModule.NETWORK_DOMAIN_NORMAL_PREDICATE;
 import static org.jclouds.dimensiondata.cloudcontrol.config.DimensionDataCloudControlComputeServiceContextModule.SERVER_DELETED_PREDICATE;
@@ -55,7 +55,7 @@
 public class BaseDimensionDataCloudControlApiLiveTest extends BaseApiLiveTest<DimensionDataCloudControlApi> {
 
    protected ApiContext<DimensionDataCloudControlApi> ctx;
-   private final Set<Module> modules = ImmutableSet.<Module>of(new ExecutorServiceModule(sameThreadExecutor()));
+   private final Set<Module> modules = ImmutableSet.<Module>of(new ExecutorServiceModule(newDirectExecutorService()));
    protected Set<String> datacenters;
 
    protected static final String PREPARED_CUSTOMER_IMAGE_ID = "fb438e00-10f8-47ac-a434-f3f9461c3a76";