dns: don't populate forwarders with DoT forwarders
DNS over TLS setup overrides global forwarder to point to Unbound, so no
need to setup regular forwarders.
Resolves: https://pagure.io/freeipa/issue/9748
Signed-off-by: Antonio Torres <antorres@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>