Bug 27421: (QA follow-up) Polishing the backgroundjob modules

Bug 27421: (QA follow-up) Polishing the backgroundjob modules

StageMARCForImport:
- Rollback in catch
- Setting progress, size or status after BatchStageMarcRecords
  in both try and catch block

ImportCommitBatch:
- Move setting size back to enqueue moment
- Rollback in catch
- Setting progress, size or status after BatchStageMarcRecords
  in both try and catch block

ImportRevertBatch:
- Move setting size back to enqueue moment
- Adding transaction/rollback to module since import routine
  does not support it. Could be moved later.
- Setting progress, size or status after BatchStageMarcRecords
  in both try and catch block

Test plan:
Run t/db_dependent/Koha/BackgroundJobs/StageMARCForImport.t
Test staging file
Bonus: Put a die statement in BatchStageMarcRecords.

Test importing batch
Bonus: Include some records with an invalid library code; this will
trigger an FK exception. (Reduce the progress from 50 to 1. If your
first record would be fine, check if it is NOT imported when the job
fails.)

Test reverting batch.
Bonus: Put a die in BatchRevertRecords.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>