Specify number of cache segments in test

Signed-off-by: Andrew Ross <andrross@amazon.com>

server/src/test/java/org/opensearch/index/store/remote/utils/TransferManagerTests.java

@@ -37,7 +37,7 @@
 
 @ThreadLeakFilters(filters = CleanerDaemonThreadLeakFilter.class)
 public class TransferManagerTests extends OpenSearchTestCase {
-    private final FileCache fileCache = FileCacheFactory.createConcurrentLRUFileCache(1024 * 1024);
+    private final FileCache fileCache = FileCacheFactory.createConcurrentLRUFileCache(1024 * 1024, 8);
     private final ExecutorService executor = Executors.newSingleThreadExecutor();
     private MMapDirectory directory;
     private BlobContainer blobContainer;