Override SimpleStepBuilder.faultTolerant() in FaultTolerantStepBuilder

Override SimpleStepBuilder.faultTolerant() in FaultTolerantStepBuilder
to prevent creation of a new FaultTolerantStepBuilder when calling
faultTolerant() on an existing FaultTolerantStepBuilder. Otherwise
configuration, like chunkListeners, are lost.

Issue #3840

spring-batch-core/src/test/java/org/springframework/batch/core/step/builder/FaultTolerantStepBuilderTests.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.batch.core.step.builder;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class FaultTolerantStepBuilderTests {
+
+    @Test
+    public void faultTolerantReturnsSameInstance() {
+        FaultTolerantStepBuilder<Object, Object> builder = new FaultTolerantStepBuilder<>(new StepBuilder("test"));
+        assertEquals(builder, builder.faultTolerant());
+    }
+}