auto rekey when unpair (#4742)
auto rekey when unpair (#4742)

(cherry picked from commit de123661ca6376125324c55ac5c5a007d913b87f)

firewalla/firewalla,firewalla/firewalla,MelvinTo/firewalla,firewalla/firewalla,MelvinTo/firewalla,MelvinTo/firewalla,firewalla/firewalla,MelvinTo/firewalla,firewalla/firewalla,MelvinTo/firewalla