Bug 33044: Return job id if there is no connection to rabbit

Bug 33044: Return job id if there is no connection to rabbit

This patch simply ensures we return the job id even if we couldn't send
the job to rabbit.

To test:
1 - In KTD: sudo service rabbitmq-server stop
2 - sudo koha-worker --stop kohadev; sudo koha-worker --queue long_tasks --stop kohadev
3 - In staff client enqueue a batch item modification - note the link to view the enqueued job has no id in the url and takes you to the main background jobs viewer
4 - Run t/db_dependent/Koha/BackgroundJob.t and notice that it fails.
5 - Apply patch
6 - Restart all
7 - Enqueue a new batch item modification
8 - Confirm the link works and has the correct id
9 - Run t/db_dependent/Koha/BackgroundJob.t; it should pass now.

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