The first offset returned by a ChronicleLogTailer can be wrong

When a Chronicle Tailer is initialized on an empty partition,
the first record appended is returned with a wrong offset like logName-00:+0 instead of logName-00:+6753252855055908865.

This is because the first position is unknown when the CQ4 file is empty (state UNINITIALIZED).

This shouldn't impact any code so far, no backport needed.