Merge pull request #440 from Hellojungle/fix#439

[ISSUE #439] fix ConsumeMessageCommand -g option

tools/src/main/java/org/apache/rocketmq/tools/command/message/ConsumeMessageCommand.java

@@ -131,7 +131,7 @@ public class ConsumeMessageCommand implements SubCommand {
         try {
             /* Group name must be set before consumer start */
             if (commandLine.hasOption('g')) {
-                String consumerGroup = commandLine.getOptionValue('b').trim();
+                String consumerGroup = commandLine.getOptionValue('g').trim();
                 defaultMQPullConsumer.setConsumerGroup(consumerGroup);
             }