KAFKA-8024; Fix `UtilsTest` failure under non-english locales (#6351)

The two digit formatting we use in `Utils.formatBytes` depends on the english locale. If run from a different locale (e.g. German), the test case fails. This patch uses english explicitly.

Reviewers: Lee Dongjin <dongjin@apache.org>, Jason Gustafson <jason@confluent.io>

clients/src/main/java/org/apache/kafka/common/utils/Utils.java

@@ -39,11 +39,12 @@ import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
-import java.nio.file.SimpleFileVisitor;
 import java.nio.file.Paths;
+import java.nio.file.SimpleFileVisitor;
 import java.nio.file.StandardCopyOption;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -53,6 +54,7 @@ import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Properties;
@@ -75,7 +77,8 @@ public final class Utils {
     private static final Pattern VALID_HOST_CHARACTERS = Pattern.compile("([0-9a-zA-Z\\-%._:]*)");
 
     // Prints up to 2 decimal digits. Used for human readable printing
-    private static final DecimalFormat TWO_DIGIT_FORMAT = new DecimalFormat("0.##");
+    private static final DecimalFormat TWO_DIGIT_FORMAT = new DecimalFormat("0.##",
+        DecimalFormatSymbols.getInstance(Locale.ENGLISH));
 
     private static final String[] BYTE_SCALE_SUFFIXES = new String[] {"B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"};