Addendum for HADOOP-14146 jdk7 support.

(cherry picked from commit 4c6184b41c)

hadoop-common-project/hadoop-auth/src/main/java/org/apache/hadoop/security/authentication/util/KerberosUtil.java

@@ -450,5 +450,10 @@ public class KerberosUtil {
     public String toString() {
       return "[tag=0x"+Integer.toHexString(tag)+" bb="+bb+"]";
     }
+
+    @Override
+    public void remove() {
+      throw new UnsupportedOperationException();
+    }
   }
 }