Bug 29510: Make objects.find call search_limited if present

Bug 29510: Make objects.find call search_limited if present

This patch makes objects.find implicitly update the passed
*$result_set* to use search_limited. This way no object leaks could
happen without noticing.

To test:
1. Apply the regression tests patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/REST/Plugin/Objects.t
=> FAIL: Tests fail because search_limited is not used
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass! Results are correctly filtered based on userenv!
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>