when parent mapping is set, fix setting routing to required

modules/elasticsearch/src/main/java/org/elasticsearch/index/mapper/xcontent/RoutingFieldMapper.java

@@ -89,7 +89,7 @@ public class RoutingFieldMapper extends AbstractFieldMapper<String> implements o
     }
 
     public void markAsRequired() {
-        this.required = required;
+        this.required = true;
     }
 
     @Override public boolean required() {