HADOOP-15681. AuthenticationFilter should generate valid date format for Set-Cookie header regardless of default Locale. Contributed by Cao Manh Dat.

hadoop-common-project/hadoop-auth/src/main/java/org/apache/hadoop/security/authentication/server/AuthenticationFilter.java

@@ -681,7 +681,7 @@ public class AuthenticationFilter implements Filter {
     if (expires >= 0 && isCookiePersistent) {
       Date date = new Date(expires);
       SimpleDateFormat df = new SimpleDateFormat("EEE, " +
-              "dd-MMM-yyyy HH:mm:ss zzz");
+              "dd-MMM-yyyy HH:mm:ss zzz", Locale.US);
       df.setTimeZone(TimeZone.getTimeZone("GMT"));
       sb.append("; Expires=").append(df.format(date));
     }