Follower does not check consistency of AppendEntries

[schuster]

If a follower has fallen very far behind, it might be the case that the leader sends it a batch of messages that starts past the end of the follower's log. In this case, the follower should reject the request, and the leader should send a new request starting at an earlier point in the log.

See section 5.3 (towards the end of that section) of the tech report for more details.

[colin-scott]

For what it's worth, I have a (non-pull-request-worthy) fix to this issue here:

NetSys/demi-applications@705f8de