Bug 27421: (QA follow-up) BatchCommitImportRecords needs param for skipping commits

Bug 27421: (QA follow-up) BatchCommitImportRecords needs param for skipping commits

When you submit a background jobs, and it fails, you do not expect
partial results in the database.
Note that when the Background feature would support a partially
completed status, things might change again.

Note that the >0 test was superfluous if you check for ^\d+$.

Test plan:
Run t/db_dependent/Koha/BackgroundJobs/StageMARCForImport.t

Note: This serves to verify that it still runs as expected.
The test plan of the following patch covers the new param.

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