Persistent log contains two entries with the same id across restarts of dlogd

[gcjenkinson]

Allow the in-kernel dlog appends to records in the log, the ids of the last record and the first record across a restart of dlogd can have the same value. This makes indexing of the log impossible for dlogd and it will result in the producer transitioning to the FINAL state at which point an assert is triggered.

Further investigation is needed to determine under what conditions this happens.