missing index after weekly restart

[mdavidsaver]

Package version 2.9.2+dfsg-17 introduced a regression involving generation of the year index when done as part of ArchiveEngine (re)start. For some reason, the file which has just become (or is becoming) the 2nd more recent is not included in the year index. The symptom is that the previous week's data is not visible.

I suspect this is a race with the new ArchiveEngine being started which was often won by the ArchiveEngine before 2.9.2+dfsg-17 made index generate faster.

This bug is blocking stabilization of 2.9.2+dfsg-18.