ipatests/test_integration/test_dnssec.py: Enable dns firewall service
    
    The dns firewall service needs to be enabled for the servers and replicas
    where dns support has not been enabled at install time. Also it is needed
    to enable the dns firewall service on the replica for migrating the dns
    server to the replica.
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Armando Neto <abiagion@redhat.com>