[kldap] Fix compilation without LDAP

Summary: Update the method signatures when not LDAP_FOUND

Test Plan: It compiles when LDAP_FOUND is not defined

Reviewers: KDE PIM, vkrause, dvratil

Reviewed By: KDE PIM, vkrause

Subscribers: kde-pim

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D26337