Bug 31325: Fix koha-preferences get

Bug 31325: Fix koha-preferences get

To reproduce:
$ perl koha/misc/admin/koha-preferences get MarcFlavour
This will output something like "HASH(0x55dd4d432840)".

To test:
Apply this patch and run the command again:
$ perl koha/misc/admin/koha-preferences get MarcFlavour
This should output something like "MARC21".

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 3f1fe4f178df3423bc95f9a288aaefdda6a6e8c0)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit 92d541ddc4e3fe53c36cee836eb6c9b33f535694)
Signed-off-by: Arthur Suzuki <arthur.suzuki@biblibre.com>