ipapython: Support openldap 2.6
While python-ldap is strict dependency of IPA in downstreams, it
is optional for IPA packages published on PyPI.
Openldap 2.6 no longer ships ldap_r-2, that makes
ipapython.dn_ctypes not working against such environments.
Thanks @abbra!
Fixes: https://pagure.io/freeipa/issue/9255
Signed-off-by: Stanislav Levin <slev@altlinux.org>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>