ddns-scripts: "now-dns.com" service fix

ddns-scripts: "now-dns.com" service fix
 - Add valid responses "good|nochg" so that ddns-script could recognize "badauth"
   error that comes with http 200 code
 - Switch url to https scheme. "now-dns.com" always returns 302 redirect
   to https:// for all plain-text http requests. Since working via default
   plain-text http is not possible anyway, forcing url to https prevents
   curl sending unencrypted plain-text credentials via basic auth

Signed-off-by: Emil Muratov <gpm@hotplug.ru>