Ignore _field_names warning in testRollupAfterRestart (elastic#115563)

Author: kkrik-es

x-pack/qa/full-cluster-restart/src/javaRestTest/java/org/elasticsearch/xpack/restart/FullClusterRestartIT.java

@@ -435,6 +435,7 @@ public void testRollupAfterRestart() throws Exception {
 
             final Request bulkRequest = new Request("POST", "/_bulk");
             bulkRequest.setJsonEntity(bulk.toString());
+            bulkRequest.setOptions(RequestOptions.DEFAULT.toBuilder().setWarningsHandler(fieldNamesFieldOk()));
             client().performRequest(bulkRequest);
 
             // create the rollup job