Bug 19845: Do not generate a password if one is filled on selfreg

Bug 19845: Do not generate a password if one is filled on selfreg

Bug 15343 allows patrons to choose their own passwords during self-registration.
But this does not work if the PatronSelfRegistrationVerifyByEmail preference is
set to "Require." If e-mail verification is required, whatever password the patron
supplied in the form is ignored, and they are given a randomly generated password
once they click on the verification link.

Test plan:
1. Make sure there is a valid e-mail stored in the KohaAdminEmailAddress preference.
2. Set PatronSelfRegistration to Allow.
3. Set PatronSelfRegistrationVerifyByEmail to Require.
3. Be sure "password" is listed in PatronSelfRegistrationBorrowerMandatoryField and
NOT listed in PatronSelfRegistrationBorrowerUnwantedField.
4. Be sure there is a valid patron category in PatronSelfRegistrationDefaultCategory.
5. Set PatronSelfRegistrationPrefillForm to "Display and prefill" so that you can see
the generated password.

Then fill out the self-registration form, include a valid e-mail address, and select
a password. Wait for the verification e-mail. Click on the link and you'll see that
the password you entered in the form is used.

Signed-off-by: Arturo <alongoria@sll.texas.gov>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>