Don't rely on positional arguments for python-kerberos calls
Upstream PyKerberos uses a different argument ordering than
from the patch that Fedora/RHEL was carrying for
authGSSClientInit().
Using named arguments provides forwards and backwards
compatibility.
https://fedorahosted.org/freeipa/ticket/5085
Reviewed-By: Tomas Babej <tbabej@redhat.com>