Automatically unload pre-defined empty zone if the forward zone is in LDAP.
    
    BIND version 9.9 automatically loads all empty zones defined
    in RFC 6303. Forwarding configuration is not honoured when it is
    applied to a empty zone. This patch automatically unloads
    empty zone if forwarding for this zone is configured in LDAP.
    
    https://fedorahosted.org/bind-dyndb-ldap/ticket/119
    
    Signed-off-by: Petr Spacek <pspacek@redhat.com>