certs: do not export CA certs in install_pem_from_p12
This fixes `kdc.crt` containing the full chain rather than just the KDC
certificate in CA-less server install.
https://pagure.io/freeipa/issue/6831https://pagure.io/freeipa/issue/6869
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>