Bug 34990: Add persistent header when sending msg to RabbitMQ

Bug 34990: Add persistent header when sending msg to RabbitMQ

Test plan:
NOTE: It is very hard to add a Koha unit test for adding this
single header when communicating to RabbitMQ via Stomp plugin.
When we would mock the send, we are only testing if perl can
pass a hashref to a subroutine ;)

Do NOT yet apply this patch.
Make sure that RabbitMQ runs.
Stop the koha-worker for long_tasks:
  koha-worker --stop --queue long_tasks myclone
Stage a MARC file.
Check queues with rabbitmqctl list_queues.
Look for: koha_myclone-long_tasks 1  (at least 1)
Stop rabbitmq (something like /etc/init.d/rabbitmq-server stop)
Start rabbitmq (/etc/init.d/rabbitmq-server start)
Check queue again with with rabbitmqctl list_queues.
Look for: koha_myclone-long_tasks 0
Your messages have been gone.

Now apply this patch.
Reiterate the former steps. But note that you will still see
a non-empty queue in the last step:
koha_myclone-long_tasks 1 (at least 1)

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