slaveReadEnable=true not work When cluster deployed on DLedger mode sometimes[Followed #2157]

[maixiaohai]

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BUG REPORT

1. Please describe the issue you observed:

• What did you do (The steps to reproduce)?
  Start cluster deployed on DLedger mode and broker config slaveReadEnable=true.

• What did you expect to see?
  When I started consumer to consume some history record which should be suggest consume from slave,
  I think the consumer will pull messages from follower node.

• What did you see instead?
  I found consumer still pull messages from leader node.

2. Please tell us about your environment:
   env

version:4.7.0
jdk 8
centos 7

some broker conf

listenPort=30911
brokerClusterName=c4tst-rocketmq-fusion
enableDLegerCommitLog=true
sendMessageThreadPoolNums=128
slaveReadEnable=true
useReentrantLockWhenPutMessage=true
transferMsgByHeap=true

3. Other information (e.g. detailed explanation, logs, related issues, suggestions how to fix, etc):
   the root cause is brokerId 1 not exist when node n0 is voted as leader. The broker id will be 0, 2, 3.

• read from slave case, left is a follower(n0) and right is the leader(n1)
  

• read from master case,left is a leader(n0) and right is the follower(n1)
  

• When I fixed the bug, read from slave case,left is a leader(n0) and right is the follower(n1)
  

[RongtongJin]

Good catch! It is indeed a bug.