Improvements to short flat handling in daily pipeline

[akremin]

There is a corner case when re-loading flats after a script crash where upon restarting the script the 1s short flat will be included with the other flats for use in producing the nightlyflat's. This corrects that by only adding a flat if it is over 100s, but still allowing the loop to continue looking for additional flats of the correct type.

This also improves the saving of tables by writing out after joint fitting. Previously the tables were only written out after a single exposure processing, so some jobs could be submitted but not saved to the table on disk before a crash. Now we write out after each joint fit.

I tested this using dry-run-level=2, which produces the tables but doesn't submit jobs. I killed the script after joint fits and found the joint jobs were written out before the script crashed (the desired new behavior). I also confirmed that the 1s flat is no longer included in the list of flats used for nightlyflat's if the script re-initializes from the tables after a crash (i.e. the corner case is now resolved).

[coveralls]

Coverage decreased (-0.01%) to 26.115% when pulling b33c7d6 on shortflatfix into e4aca0e on master.