Build: fix KDC proxy installation and remove unused kdcproxy.conf
The only useful file is /etc/ipa/kdcproxy/kdcproxy.conf so I've removed
the other copy of the file in /usr.
https://fedorahosted.org/freeipa/ticket/6418
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Christian Heimes <cheimes@redhat.com>