- + A slave (presumably a recently restarted master) receiving a
- LASTSEEN message sends a zero basetime ping (as sent by the master
- on clean shutdown).
+ + Any PING seen from a master forces an election (rather than just
+ where basetime is zero).
+ + A slave which receives a LASTSEEN message (presumably a restarted
+ master) sends back a ping, indicating that it's not the master.