DbColumDefault must be returned although if individual columnDefinition is specified (cases no DDL change)

We support optional platform columnDefinitions now. E.g. "db2;clob(64M);" - so we must not ignore @DbDefault for all other platforms

ebean-core/src/main/java/io/ebeaninternal/server/deploy/BeanProperty.java

@@ -1004,7 +1004,7 @@ public class BeanProperty implements ElPropertyValue, Property, STreeProperty {
    * Return the DB column default to use for DDL.
    */
   public String dbColumnDefault() {
-    return dbColumnDefn != null ? null : dbColumnDefault;
+    return dbColumnDefault;
   }
 
   /**