MockRestServiceServer clears failed requests map

Closes gh-24486

spring-test/src/main/java/org/springframework/test/web/client/AbstractRequestExpectationManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -199,6 +199,7 @@ public abstract class AbstractRequestExpectationManager implements RequestExpect
 	public void reset() {
 		this.expectations.clear();
 		this.requests.clear();
+		this.requestFailures.clear();
 	}