avoid a deadlock the fetch_lock code. The deadlock could happen when

avoid a deadlock the fetch_lock code. The deadlock could happen when
a client held the chainlock, and the daemon received a dmaster reply
at the same time. The daemon would not be able to process the dmaster
reply, due to the lock, but the fetch lock cannot make progres until
the dmaster reply is processed.

The solution is to not hold the lock in the client while talking to
the daemon. The client has to retry the lock after the record has
migrated. This means that forward progress is not guaranteed. We'll
have to see if that matters in practice.