Suppress extras FS on caching directory tests

This filesystem needs to be suppressed during these tests because it
adds random files to the directory upon directory creation. That means
that the size of these directories is off from what we expect them to
be. Rather than loosening the assertion which could hide bugs on real
directories, this commit suppresses this file system in this test suite.

server/src/test/java/org/elasticsearch/index/store/ByteSizeCachingDirectoryTests.java

@@ -23,11 +23,13 @@
 import org.apache.lucene.store.FilterDirectory;
 import org.apache.lucene.store.IOContext;
 import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.util.LuceneTestCase;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.test.ESTestCase;
 
 import java.io.IOException;
 
+@LuceneTestCase.SuppressFileSystems("ExtrasFS")
 public class ByteSizeCachingDirectoryTests extends ESTestCase {
 
     private static class LengthCountingDirectory extends FilterDirectory {