Bug 27729: Fix use of grep and split in CheckReserves

Bug 27729: Fix use of grep and split in CheckReserves

A few lines of code were added to CheckReserves containing the wrong
use of two perl functions: grep and split on bug 25232.
A test was added even making these things pass.

Test plan:
Run t/db../Holds.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>