[ROCKETMQ-31] Fix 'No such file or directory' warning for...

[ROCKETMQ-31] Fix 'No such file or directory' warning for /Users/zhouxinyu/rmq_bk_gc.log, closes apache/incubator-rocketmq#29

bin/mqbroker

@@ -42,6 +42,4 @@ fi
 
 export ROCKETMQ_HOME
 
-rm -f $HOME/rmq_bk_gc.log.bac
-cp $HOME/rmq_bk_gc.log $HOME/rmq_bk_gc.log.bac
 sh ${ROCKETMQ_HOME}/bin/runbroker.sh org.apache.rocketmq.broker.BrokerStartup $@