FIX: do not hit database if inherited entity has no children (#974)

* FIX: do not hit database if inherited entity has no children

* ADD: Testcase for creating references of inherited beans

src/main/java/io/ebeaninternal/server/core/DefaultServer.java

@@ -612,7 +612,7 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     }
 
     InheritInfo inheritInfo = desc.getInheritInfo();
-    if (inheritInfo == null) {
+    if (inheritInfo == null || inheritInfo.getChildren().isEmpty()) {
       return (T) desc.contextRef(pc, null, false, id);
     }
 

src/main/java/io/ebeaninternal/server/deploy/InheritInfo.java

@@ -164,7 +164,14 @@ public class InheritInfo {
   public BeanProperty[] localProperties() {
     return descriptor.propertiesLocal();
   }
-
+  
+  /**
+   * Return the children.
+   */
+  public ArrayList<InheritInfo> getChildren() {
+    return children;
+  }
+  
   /**
    * Get the bean property additionally looking in the sub types.
    */