[feature] Switch the leader to the updated node before updating the leader.

[runkecheng]

trafficstars

Is your feature request related to a problem? Please describe.

3 replicas (1 leader, 2 followers,), updating:

before:

1. update(restart) a follower
2. update(restart) another follower
3. update(restart) leader, re -elected.

If active switch leader:

1. update(restart) a follower
2. update(restart) another follower
3. switch leader to an updated node
4. update(restart) leader (need not re-elect)

Describe the solution you'd like

Describe alternatives you've considered

Additional context