Bug 25723: Update cache flushing calls

Bug 25723: Update cache flushing calls

This patch updates the previous single_holidays and exeption_holidays
cache flushing calls to match the new cache key structure of the updated
routines.

Signed-off-by: Emma Perks <Emma.Perks2@uhb.nhs.uk>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 61141c28b0fcbbb021371bb4c2dd8e818aec0691)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>