Bug 14195: TestBuilder - A random string should not be longer than the DB field

Bug 14195: TestBuilder - A random string should not be longer than the DB field

t::lib::TestBuilder::_gen_text does not use correctly the regex and the
max parameter to generate the random string (String::Random).

This can cause future tests to fail.

http://bugs.koha-community.org/show_bug.cgi?id=14195
Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Script tested, problem occurs, patch fixes it.
Bad number on commit subject
No errors

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>