Rename file name

Author: hfutatzhanghb

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/async/TestRouterAsyncClientRejectOverload.java renamed to hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/async/TestRouterAsyncRpcWhenNamenodeFailover.java

@@ -34,7 +34,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-public class TestRouterAsyncClientRejectOverload {
+public class TestRouterAsyncRpcWhenNamenodeFailover {
 
   private StateStoreDFSCluster cluster;