Fix logic around config. variable 'nuxeo.user.registration.force.validation.non.existing'

When configuration variable nuxeo.user.registration.force.validation.non.existing is set to true, it does not seem to force the validation.
Check in platform & addon nuxeo-platform-user-registration's code.

RegistrationRules#allowDirectValidationForNonExistingUser being the method to get the value of configuration variable nuxeo.user.registration.force.validation.non.existing, here is the code in UserInvitationComponent#submitRegistrationRequest that determines if the invitation validation must be forced:

        RegistrationRules registrationRules = getRegistrationRules(configurationName);
        boolean byPassAdminValidation = autoAccept;
        byPassAdminValidation |= userAlreadyExists && registrationRules.allowDirectValidationForExistingUser();
        byPassAdminValidation |= registrationRules.allowDirectValidationForExistingUser()
                && registrationRules.allowDirectValidationForNonExistingUser();
        if (byPassAdminValidation) {
            // Build validationBaseUrl with nuxeo.url property as request is not
            // accessible.
            if (!additionnalInfo.containsKey("enterPasswordUrl")) {
                additionnalInfo.put("enterPasswordUrl", buildEnterPasswordUrl(currentConfig));
            }

if the goal of configuration variable nuxeo.user.registration.force.validation.non.existing is to force the invitation validation, it does not show in the code.

FYI The default value returned by RegistrationRules#allowDirectValidationForExistingUser is false.