Bug 25527: Initialize the logger when required

Bug 25527: Initialize the logger when required

In an OO package, the logger initialization should happen in the
constructor. This is not an OO package and the initialization is
happening on loading it. This is a wrong behaviour and certainly breaks
in environments where initialization cannot happen (package building,
for example). There could be several options to solve this, as it is
used in a single sub on this package, I opted for initializing on that
sub.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>