Catch DNS exceptions during emptyzones named.conf upgrade
    
    For some reasons named may not be runnig and this cause fail of this
    upgrade step. This step is not critical so only ERROR message with
    recommendation is shown.
    
    https://fedorahosted.org/freeipa/ticket/6205
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>