Recover client from server restarts when handling batons?

Currently, I think that when a client holds a server-issued baton and attempts to send it back after a server restart, the request fails with a BatonInvalid error. This error breaks the client's workflow and requires manual intervention.

If this turns out to be the case, let's fix that so thatif a BatonInvalid error occurs and no transaction is in progress, the client should:

• Automatically restart the stream
• Obtain a new baton from the server
• Continue normal operation