Bug 21336: Introduce administrative lockout

Bug 21336: Introduce administrative lockout

As a preparation for Koha::Patron->lock, we add the concept of administrative
lockout. The account is locked just as it would have been by too much
failed login attempts.
This is handled by a negative value in borrowers.login_attempts.

Test plan:
Run t/db_dependent/Auth.t

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>