DNS upgrade: change forwarding policy to = only for conflicting forward zones
This change is necessary to override automatic empty zone configuration
in latest BIND and bind-dyndb-ldap 9.0+.
This procedure is still not complete because we need to handle global
forwarders too (in LDAP and in named.conf on each server).
https://fedorahosted.org/freeipa/ticket/5710
Reviewed-By: Martin Basti <mbasti@redhat.com>