agccActor sometimes fails completing the exposure

As reported to INSTRM-2573, agccActor sometimes fails completing the exposure routine with centroiding. 

This is just for recording a fix,because implementation was done already (under INSTRM-2698 name).

Comment on Slack by Craig

On INSTRM-2698, slightly cleaned up/fixed/annotated the agccActor per-camera exposure thread, to either allow it to complete failed partial exposures, or at least report something about the error. I wanted to add a more complete exception handling, but got cold feet. Tagged and installed 1.2.16 at the tip of the unmerged INSTRM-2698. Not sure where this is running (could not log on to pfs-data@agcc), so have not (yet) restarted it. [ Ah, agcc2, got it. New version started. ]