Bug 19003: Add a TestBuilder default for borrowers.login_attempts

Bug 19003: Add a TestBuilder default for borrowers.login_attempts

Bug 18314 causes t/db/SIP/Message.t to fail (quite often) since
TestBuilder fills login_attempts with a random number. (Note: Only
when FailedLoginAttempts is non-zero.)
Trivial fix: TestBuilder should have a zero default for login_attempts.

Test plan:
Do not yet apply this patch.
Set pref FailedLoginAttempts to say 3.
Run t/db_dependent/SIP/Message.t. Might fail on the password test (CQ).
Apply this patch.
Run t/db_dependent/SIP/Message.t again. Does not fail anymore.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>