Bug 15014: Returns 0 if everything went fine

Bug 15014: Returns 0 if everything went fine

Be kind and return 0 if the sample file has been generated correctly.
Otherwise you are a bad guy and you make Plack returns an internal error
(exited nonzero: 1 at /home/vagrant/kohaclone/tools/import_borrowers.pl line 390.)

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Works as expected
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Works as expected here too.

(cherry picked from commit 314f3e22d969b05ffd0590153707fd0c673987be)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>