Bug 27600: Add unit test

Bug 27600: Add unit test

This patch adds a basic unit test to catch the case where patron_pwd is
sent to renew_all as an empty string.

Test plan
1/ Run t/db_dependent/SIP/ILS.t and watch it fail
2/ Apply second patch
3/ Re-run the above test and watch it pass.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 3724e1646876ba14b296132e1f93e15df7a0a9e2)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>