Make old/new BeaconChainController easily interchangeable

services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/AbstractBeaconChainController.java

@@ -0,0 +1,7 @@
+package tech.pegasys.teku.services.beaconchain;
+
+import tech.pegasys.teku.service.serviceutils.Service;
+
+public abstract class AbstractBeaconChainController extends Service implements BeaconChainControllerFacade {
+
+}

services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/BeaconChainController.java

@@ -38,7 +38,7 @@
  * initialization behavior (see {@link BeaconChainControllerFactory}} however this class may change
  * in a backward incompatible manner and either break compilation or runtime behavior
  */
-public class BeaconChainController extends Service implements BeaconChainControllerFacade {
+public class BeaconChainController extends AbstractBeaconChainController {
 
   private static final Logger LOG = LogManager.getLogger();
 

services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/BeaconChainControllerOld.java

@@ -215,7 +215,7 @@
  * initialization behavior (see {@link BeaconChainControllerFactory}} however this class may change
  * in a backward incompatible manner and either break compilation or runtime behavior
  */
-public class BeaconChainControllerOld extends Service implements BeaconChainControllerFacade {
+public class BeaconChainControllerOld extends AbstractBeaconChainController {
 
   private static final Logger LOG = LogManager.getLogger();
 

services/beaconchain/src/main/java/tech/pegasys/teku/services/beaconchain/BeaconChainService.java

@@ -19,7 +19,7 @@
 
 public class BeaconChainService extends Service implements BeaconChainServiceFacade {
 
-  private final BeaconChainController controller;
+  private final AbstractBeaconChainController controller;
 
   public BeaconChainService(
       final ServiceConfig serviceConfig, final BeaconChainConfiguration beaconConfig) {
@@ -38,7 +38,7 @@ protected SafeFuture<?> doStop() {
   }
 
   @Override
-  public BeaconChainController getBeaconChainController() {
+  public BeaconChainControllerFacade getBeaconChainController() {
     return controller;
   }
 }