Bug 18731: Use the stashed koha.embed in objects.search

Bug 18731: Use the stashed koha.embed in objects.search

This patch makes the objects.search helper use the koha.embed structure
that is embedded in the authenticate_api_request step.

This way, any controller using it will benefit from automatic embed
handling.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/REST/Plugin/Objects.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>