HADOOP-9844. NPE when trying to create an error message response of SASL RPC

This closes #55

Change-Id: I10a20380565fa89762f4aa564b2f1c83b9aeecdc
Signed-off-by: Akira Ajisaka <aajisaka@apache.org>
(cherry picked from commit 07530314c2130ecd1525682c59bf51f15b82c024)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/IpcException.java

@@ -26,9 +26,8 @@ import java.io.IOException;
  */
 public class IpcException extends IOException {
   private static final long serialVersionUID = 1L;
-  
-  final String errMsg;
+
   public IpcException(final String err) {
-    errMsg = err; 
+    super(err);
   }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java

@@ -1948,7 +1948,7 @@ public abstract class Server {
     private void doSaslReply(Exception ioe) throws IOException {
       setupResponse(authFailedCall,
           RpcStatusProto.FATAL, RpcErrorCodeProto.FATAL_UNAUTHORIZED,
-          null, ioe.getClass().getName(), ioe.getLocalizedMessage());
+          null, ioe.getClass().getName(), ioe.toString());
       sendResponse(authFailedCall);
     }
 
@@ -2307,7 +2307,8 @@ public abstract class Server {
         final RpcCall call = new RpcCall(this, callId, retry);
         setupResponse(call,
             rse.getRpcStatusProto(), rse.getRpcErrorCodeProto(), null,
-            t.getClass().getName(), t.getMessage());
+            t.getClass().getName(),
+            t.getMessage() != null ? t.getMessage() : t.toString());
         sendResponse(call);
       }
     }