[Test] Do not use ExtrasFS for fileSettingsServiceTests (#123578)

The tests expect tightly controlled set of files and should not see
random extra files.

server/src/test/java/org/elasticsearch/reservedstate/service/FileSettingsServiceTests.java

@@ -12,6 +12,7 @@ package org.elasticsearch.reservedstate.service;
 import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.apache.lucene.tests.util.LuceneTestCase;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.cluster.ClusterChangedEvent;
 import org.elasticsearch.cluster.ClusterName;
@@ -84,6 +85,7 @@ import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
+@LuceneTestCase.SuppressFileSystems("ExtrasFS")
 public class FileSettingsServiceTests extends ESTestCase {
     private static final Logger logger = LogManager.getLogger(FileSettingsServiceTests.class);
     private Environment env;