Unify storing certificates in LDAP
Recent certificate refactoring left the system in a state where
the certificates are somewhere converted to DER format, somewhere
directly sent to ipaldap as IPACertificate objects. The latter
is the desirable way, make sure it's the one commonly used.
https://pagure.io/freeipa/issue/4985
Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>