Add missing static imports for JUnit 5 assertions in HDFS module

Added missing static imports:
- import static org.junit.jupiter.api.Assertions.fail;
- import static org.junit.jupiter.api.Assertions.assertTrue;

These were previously imported from JUnit 4 and are needed for the
fail() and assertTrue() method calls in the test code.

Author: gnodet

commons-vfs2-hdfs/src/test/java/org/apache/commons/vfs2/provider/hdfs/HdfsFileProviderTestCase.java

@@ -17,6 +17,8 @@
 package org.apache.commons.vfs2.provider.hdfs;
 
 import static org.apache.commons.vfs2.VfsTestUtils.getTestDirectoryFile;
+import static org.junit.jupiter.api.Assertions.fail;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.File;
 import java.io.IOException;