Bug 11112: (follow-up) add FIXME

Bug 11112: (follow-up) add FIXME

The caching introduced by the main patch is not ideal
as it won't work correctly if a persistance engine is used.

However, I have good reason to expect that bug 8089 will
be worked on (because I'm going to do it) so that Koha::Cache
can be used for this prior to the release of 3.16.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit aca1f5f6a9c5fb58e62ab060c272eadc287bb167)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>