Bug 27012: Fix incorrect SQL syntax in hold merging

Bug 27012: Fix incorrect SQL syntax in hold merging

If you merge two records with holds in them following error happens
without this patch:

[WARN] DBD::mysql::st execute failed: called with 4 bind variables when 3 are needed [for Statement "SELECT * FROM reserves WHERE biblionumber = ? AND (found <> ? AND found <> ? OR found is NULL) ORDER BY reservedate ASC" with ParamValues: 0=Null!, 1=Null!, 2=Null!] at /kohadevbox/koha/C4/Reserves.pm line 2002.

To test:
   1) Notice prove t/db_dependent/Reserves.t fails with above error
   2) Apply patch
   3) Notice prove t/db_dependent/Reserves.t passes

Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>