In order to minimize this change while keeping a simple version of the
behavior, we set `lastOk` to the current time less the intial server
connection timeout. If the client starts and never contacts the
server, it will stop all configured tasks after the initial server
connection grace period, on the assumption that we've been out of
touch longer than any configured `stop_after_client_disconnect`.
The more complex state behavior might be justified later, but we
should learn about failure modes first.
- track lastHeartbeat, the client local time of the last successful
heartbeat round trip
- track allocations with `stop_after_client_disconnect` configured
- trigger allocation destroy (which handles cleanup)
- restore heartbeat/killable allocs tracking when allocs are recovered from disk
- on client restart, stop those allocs after a grace period if the
servers are still partioned
