Bug 35819: Add simple delay

Here I add 500 ms. In my testing with the 1s sleep from the test
plan, I might see one or two 'not found' lines. Obviously things
depend on the time needed before the txn commits. But it will
reduce a flood of these messages.

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

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 0feb10df7f)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit b1efcf3d15)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>

misc/workers/background_jobs_worker.pl

@@ -59,6 +59,7 @@ use Try::Tiny;
 use Pod::Usage;
 use Getopt::Long;
 use Parallel::ForkManager;
+use Time::HiRes;
 
 use C4::Context;
 use Koha::Logger;
@@ -134,6 +135,7 @@ while (1) {
 
                 # nack to force requeue
                 $conn->nack( { frame => $frame, requeue => 1 } );
+                Time::HiRes::sleep(0.5);
                 next;
             }
             $conn->ack( { frame => $frame } );