Bug 27928: FindDuplicate should use simple_search_compat

Bug 27928: FindDuplicate should use simple_search_compat

This patch switches from calling SimpleSearch directly to using the compat
method so that Elastic is used when it is the chosen search engine

To test:
 1 - Set SearchEngine syspref to 'Zebra'
 2 - Add a suggestion with an existing title, e.g.:
   'E street shuffle'
 3 - Confirm you get a duplication warning
 4 - Change SearchEngine to ES
 5 - Repeat get same warning
 6 - sudo koha-zebra --stop
    'ps aux | grep zebra'  to confirm they are stoped
    'sudo pkill -9 zebra' if they arent;
 7 - Repeat suggestion - no duplication warning (because zebra returns nothing)
 8 - Delete the suggestion
 9 - Apply patches
10 - Restart all the things, stop zebra
11 - Repeat suggestion
12 - Successful warning from ES
13 - prove -v t/db_dependent/Search.t

Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>