Use mod_auth_gssapi instead of mod_auth_kerb.

https://fedorahosted.org/freeipa/ticket/4190

Reviewed-By: Jan Cholasta <jcholast@redhat.com>
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Simo Sorce <ssorce@redhat.com>

init/systemd/ipa.conf.tmpfiles

@@ -1,2 +1,3 @@
 d /var/run/ipa_memcached 0700 apache apache
 d /var/run/ipa 0700 root root
+d /var/run/httpd/clientcaches 0700 apache apache