Bug 29503: Make GET /patrons use Koha::Patrons->search_limited

Bug 29503: Make GET /patrons use Koha::Patrons->search_limited

This patch makes the controller method use Koha::Patrons->search_limited
so filters based on configuration and permissions apply when fetching
patrons.

To test:
1. Apply the regression tests patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/patrons.t
=> FAIL: Boo, you get more patrons than you should
3. Apply the patch
4. Repeat 2
=> SUCCESS: Yay! Things are filtered as expected (i.e. using
Koha::Patron->libraries_where_can_see_patrons)
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: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>