The ConfChange fix crashes WAL replay because it assumed the node
always exists. Additionally, restart on a single node cluster
would deadlock because it had the wrong raft HardState.
To fix, replay path now goes through the regular raft loop.
Fixes#4474
Add a channel over which we can propose cluster config changes to
raft. In an upcoming commit we'll add an HTTP endpoint that sends config
changes over this channel.
deadlock if no leader; node selects on propc=nil and writes to Ready,
client blocks on propC in same select as Ready reader, and so progress
of raft state machine deadlocks.
