Bug 35111: Ignore SIGPIPE in background jobs worker

Bug 35111: Ignore SIGPIPE in background jobs worker

This change explicitly ignores SIGPIPE signals in the background jobs
worker.

Daemons like Starman ignore SIGPIPE so it makes sense to explicitly set this.
Differences in the inner workings of MySQL vs MariaDB client libraries have yielded
different behaviours in automatic reconnections and potentially SIGPIPE handling,
so this helps to make the overall behaviour more consistent.

Test plan:
0. Apply patch and run "restart_all"
1. Go to http://localhost:8081/cgi-bin/koha/catalogue/detail.pl?biblionumber=29
2. Click "Save" > "MARCXML"
3. Go to http://localhost:8081/cgi-bin/koha/tools/stage-marc-import.pl
4. Click "Choose file", choose the MARCXML file, click "Upload file"
5. Click "Stage for import"
6. Note the job is marked as "100% Finished"

7. In a separate window run "docker restart koha-db-1"
8. Repeat steps 3-5 for uploading file and running stage for import
9. Note that the job is marked as "100% Finished" as you'd expect

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
[EDIT] Added comment on the SIG PIPE line.
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>